Web viewThe force of friction between the brake pads and the steel discs gradually stops the car

03 Forces and Braking

291 minutes

291 marks

Q1. A car travels along a level road at 20 metres per second.

(a) Calculate the distance travelled by the car in 4 seconds.

(Show your working.)

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(b) When the brake pedal of the car is pushed, brake pads press against very hard steel discs.

The force of friction between the brake pads and the steel discs gradually stops the car.

What two effects does using the brakes have on the brake pads and wheel discs?

1 ..........................................................................................................................

2 ..........................................................................................................................(3)

(Total 6 marks)

Q2.

(a) A driver may have to make an emergency stop.

Stopping distance = thinking distance + braking distance.

Give three different factors which affect the thinking distance or the braking distance. In your answer you should explain what effect each factor has on the stopping distance.

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(b) Complete the following sentences by writing in the two missing words.

Acceleration is the rate of change of .............................................................. .

The acceleration of a car depends on the force applied by the engine and the

........................................... of the car.(2)

(c) A car moves because of the force applied by the engine.

Name two other forces which act on the car when it is moving. Give the direction in whicheach of these factors acts.

1. Name of force ........................................................................................................

Direction of this force ...........................................................................................

2. Name of force ........................................................................................................

Direction of this force ........................................................................................... (4)

(d) Complete the following sentence by writing in the missing word.

The velocity of a car is its speed in a particular .......................................................(1)

(Total 13 marks)

Q3. (a) The model bus is being pushed on a table.

(i) At first the pushing force does not make the model bus move. Explain why.

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...........................................................................................................................(1)

(ii) Write down two things that happen as the pushing force increases.

1 ........................................................................................................................

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2 ........................................................................................................................

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(iii) Complete the formula by choosing the correct words from the box.

acceleration distance moved force appliedspeed time taken

Work done onthe model bus = ...................................... × ......................................

(2)

(b) In this situation, the car driver needs to stop the car in the shortest possible distance.

(i) Complete the table by putting ticks ( ) to show which factors would make the stopping distance greater. The first one has been done for you.

Factor Tick ( ) makes stoppingdistance greater

brakes are old and worn

car is travelling fast

driver has been drinking alcohol

four new tyres are fitted

hot, dry, sunny weather

ice on the road

(3)

(ii) Complete the sentence by writing the correct words in the spaces.

The car will skid if the braking force is too big compared with the friction between

the car’s .................................... and the .................................... .(1)

(Total 9 marks)

Q4. This question is about a car travelling through a town.

(a) The graph shows how far the car travelled and how long it took.

(i) Between which points was the car travelling fastest? Tick ( ) your answer.

Points Tick ( )

A – B

B – C

C – D

D – E

E – F

(1)

(ii) Between which points was the car stationary?

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...........................................................................................................................(1)

(b) Complete the sentences by writing the correct words in the spaces.

When a car has to stop, the overall stopping distance is greater if:

• the car is poorly maintained;

• there are adverse weather conditions;

• the car is travelling ................................ ;

• the driver’s reactions are ................................ .

Also, the greater the speed of the car, then the greater the braking ................................

needed to stop in a certain time.(3)

(Total 5 marks)

Q5. The diagram below shows the thinking distances, braking distances and total stopping distances at different speeds.

(a) Look at the total stopping distances at each speed.

Complete the sentence by choosing the correct words from the box.

distance force mass time

The total stopping distance depends on the distance the car travels during the

driver’s reaction ............................. and under the braking ................................ .(2)

(b) Give three other factors that could cause the total stopping distance of a car to be greater. Do not give the factors in Figure 1.

1 .................................................................................................................................

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2 .................................................................................................................................

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(Total 5 marks)

Q6.

(a) The van shown above has a fault and leaks one drop of oil every second.

The diagram below shows the oil drops left on the road as the van moves from W to Z.

Describe the motion of the van as it moves from:

W to X .......................................................................................................................

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X to Y ........................................................................................................................

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Y to Z ........................................................................................................................

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(b) The van was driven for 20 seconds at a speed of 30m/s.

Calculate the distance travelled.

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Distance .................... m(2)

(c) The van was travelling at 30m/s. It slowed to a stop in 12 seconds.

Calculate the van’s acceleration.

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Acceleration .................... m/s²(3)

(d) The driver and passenger wear seatbelts. Seatbelts reduce the risk of injury.

Explain how seatbelts reduce the risk of injury.

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(Total 12 marks)

Q7. The Highway Code gives tables of the shortest stopping distances for cars travelling at various speeds. An extract from the Highway Code is given below.

thinking distance + braking distance = total stopping distance

(a) A driver’s reaction time is 0.7 s.

(i) Write down two factors which could increase a driver’s reaction time.

1 .........................................................................................................................

2 .........................................................................................................................(2)

(ii) What effect does an increase in reaction time have on:

A thinking distance; ..........................................................................................

B braking distance; ...........................................................................................

C total stopping distance? .................................................................................(3)

(b) Explain why the braking distance would change on a wet road.

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(c) A car was travelling at 30 m/s. The driver braked. The graph below is a velocity-time graph showing the velocity of the car during braking.

Calculate:

(i) the rate at which the velocity decreases (deceleration);

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Rate .......................... m/s²(2)

(ii) the braking force, if the mass of the car is 900 kg;

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Braking force ............................... N(2)

(iii) the braking distance.

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Braking distance .............................. m(2)

(Total 13 marks)

Q8. A car driver sees a dog on the road ahead and has to make an emergency stop.

The graph shows how the speed of the car changes with time after the driver first sees the dog.

(a) Which part of the graph represents the “reaction time” or “thinking time” of the driver?

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(b) (i) What is the thinking time of the driver? Time ........................ seconds(1)

(ii) Calculate the distance travelled by the car in this thinking time.

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Distance ..................................... m(3)

(c) Calculate the acceleration of the car after the brakes are applied.

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Acceleration ............................................(4)

(d) Calculate the distance travelled by the car during braking.

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Distance ................................................ m(3)

(e) The mass of the car is 800 kg. Calculate the braking force.

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Braking force ........................................ N(3)

(Total 15 marks)

Q9. A driver is driving along a road at 30 m/s. The driver suddenly sees a large truck parked across the road and reacts to the situation by applying the brakes so that a constant braking force stops the car. The reaction time of the driver is 0.67 seconds, it then takes another 5

seconds for the brakes to bring the car to rest.

(a) Using the data above, draw a speed-time graph to show the speed of the car from the instant the truck was seen by the driver until the car stopped.

(5)

(b) Calculate the acceleration of the car whilst the brakes are applied.

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Answer = .................................... m/s2

(3)

(c) The mass of the car is 1500 kg. Calculate the braking force applied to the car.

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Answer = .................................... N(3)

(d) The diagrams below show what would happen to a driver in a car crash.

(i) Explain why the driver tends to be thrown towards the windscreen.

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(ii) During the collision the front end of the car becomes crumpled and buckled. Use this information to explain why such a collision is described as “inelastic”.

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(iii) The car was travelling at 30 m/s immediately before the crash. Calculate the energy which has to be dissipated as the front of the car crumples.

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(Total 19 marks)

Q10. When a car driver has to react and apply the brakes quickly, the car travels some distance before stopping. Part of this distance is called the “thinking distance”. This is how far the car travels while the driver reacts to a dangerous situation.

The table below shows the thinking distance (m) for various speeds (km/h).

Thinking distance (m) 0 9 12 15

Speed (km/h) 0 48 64 80

(a) On the graph paper below, draw a graph of the thinking distance against speed.

(2)

(b) Describe how thinking distance changes with speed.

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.....................................................................................................................................(1)

(c) The time the driver spends thinking before applying the brakes is called the “thinking time”.

A driver drank two pints of lager. Some time later the thinking time of the driver was measured as 1.0 seconds.

(i) Calculate the thinking distance for this driver when driving at 9 m/s.

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Answer ............................................ m(1)

(ii) A speed of 9 m/s is the same as 32 km/h. Use your graph to find the thinking distance at 32 km/h for a driver who has not had a drink.

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Answer ............................................ m(1)

(iii) What has been the effect of the drink on the thinking distance of the driver?

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...........................................................................................................................(1)

(Total 6 marks)

Q11. The diagram shows an orbiter, the reusable part of a space shuttle. The data refers to a typical flight.

(a) (i) What name is given to the force which keeps the orbiter in orbit around the Earth?

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(ii) Use the following equation to calculate the kinetic energy, in joules, of the orbiter

while it is in orbit.

kinetic energy = ½ mv2

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Kinetic energy = ............................. joules(2)

(iii) What happens to most of this kinetic energy as the orbiter re-enters the Earth’s atmosphere?

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(b) After touchdown the orbiter decelerates uniformly coming to a halt in 50 s.

(i) Give the equation that links acceleration, time and velocity.

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(ii) Calculate the deceleration of the orbiter. Show clearly how you work out your answer and give the unit.

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Deceleration = ...............................(2)

(c) (i) Give the equation that links acceleration, force and mass.

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(ii) Calculate, in newtons, the force needed to bring the orbiter to a halt. Show clearly how you work out your answer.

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Force = ............................ newtons(1)

(Total 9 marks)

Q12. (a) The diagram shows the horizontal forces that act on a moving motorbike.

(i) Describe the movement of the motorbike when force A equals force B.

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...........................................................................................................................(2)

(ii) What happens to the speed of the motorbike if force B becomes smaller than force A?

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(b) The graph shows how the velocity of a motorbike changes when it is travelling along a straight road.

(i) What was the change in velocity of the motorbike in the first 5 seconds?

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(ii) Write down the equation which links acceleration, change in velocity and time taken.

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(iii) Calculate the acceleration of the motorbike during the first 5 seconds.Show clearly how you work out your answer and give the unit.

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Acceleration = .............................................(3)

(c) A car is travelling on an icy road.

Describe and explain what might happen to the car when the brakes are applied.

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(d) Name three factors, other than weather conditions, which would increase the overall stopping distance of a vehicle.

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(Total 13 marks)

Q13. A car and a bicycle are travelling along a straight road. They have stopped at road works.

The graph shows how the velocity of the car changes after the sign is changed to GO.

(a) Between which two points on the graph is the car moving at constant velocity?

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(b) Between which two points on the graph is the car accelerating?

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(c) Between the sign changing to GO and the car starting to move, there is a time delay. This is called the reaction time.

(i) What is the reaction time of the car driver?

Reaction time = ................................. seconds(1)

(ii) Which one of the following could increase the reaction time of a car driver? Tick the box next to your choice.

Drinking alcohol

Wet roads

Worn car brakes (1)

(d) The cyclist starts to move at the same time as the car. For the first 2 seconds the cyclist’s acceleration is constant and is greater than that of the car.

Draw a line on the graph to show how the velocity of the cyclist might change during the first 2 seconds of its motion.

(2)(Total 6 marks)

Q14. (a) A car driver takes a short time to react to an emergency before applying the brakes. The distance the car will travel during this time is called the ‘thinking distance’.

The graph shows how the thinking distance of a driver depends on the speed of the car.

(i) What is the connection between thinking distance and speed?

..........................................................................................................................(1)

(ii) Many people drive while they are tired.

Draw a new line on the graph to show how thinking distance changes with speed for a tired driver.

(1)

(iii) The graph was drawn using data given in the Highway Code.

Do you think that the data given in the Highway Code is likely to be reliable?

Draw a ring around your answer.

Yes No Maybe

Give a reason for your answer.

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(b) The distance a car travels once the brakes are applied is called the ‘braking distance’.

(i) What is the relationship between thinking distance, braking distance and stopping

distance?

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(ii) State two factors that could increase the braking distance of a car at a speed of15 m/s.

1 .......................................................................................................................

2 .......................................................................................................................(2)

(Total 6 marks)

Q15. (a) A car driver makes an emergency stop.

The chart shows the ‘thinking distance’ and the ‘braking distance’ needed to stop the car.

Calculate the total stopping distance of the car.

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Stopping distance = ................................................. m(1)

(b) The graph shows how the braking distance of a car driven on a dry road changes with the car’s speed.

The braking distance of the car on an icy road is longer than the braking distance of the car on a dry road.

(i) Draw a new line on the graph to show how the braking distance of the car on an icy road changes with speed.

(2)

(ii) Which two of the following would also increase the braking distance of the car?

Put a tick ( ) next to each of your answers.

rain on the road

the driver having drunk alcohol

car brakes in bad condition

the driver having taken drugs (2)

(c) The thinking distance depends on the driver’s reaction time.

The table shows the reaction times of three people driving under different conditions.

Car driver Condition Reaction timein seconds

A Wide awake with no distractions 0.7

B Using a hands-free mobile phone 0.9

C Very tired and listening to music 1.2

The graph lines show how the thinking distance for the three drivers, A, B and C, depends on how fast they are driving the car.

(i) Match each graph line to the correct driver by writing A, B or C in the box next to the correct line.

(2)

(ii) The information in the table cannot be used to tell if driver C’s reaction time is increased by being tired or by listening to music.

Explain why.

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(Total 9 marks)

(i) How many hours does it take for the count rate to fall from 300 counts per minute to 150 counts per minute?

Time = .................................................. hours(1)

(ii) What is the half-life of technetium-99?

Half-life = ............................................. hours(1)

(Total 7 marks)

Q16. The diagram shows the horizontal forces acting on a car travelling along a straight road.

(a) Complete the following sentences by drawing a ring around the correct word in each box.

(i) When the driving force equals the drag force, the speed of the car is

decreasing

constant

increasing

(1)

(ii) Putting the brakes on transforms the car’s kinetic energy mainly into

heat

light

sound

(1)

(b) The charts, A, B and C give the thinking distance and the braking distance for a car driven under different conditions.

(i) Draw straight lines to match each chart to the correct conditions.

Draw only three lines.

(2)

(ii) The three charts above all apply to dry road conditions.

How would the braking distances be different if the road were wet?

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...........................................................................................................................(1)

(Total 5 marks)

Q17. (a) The diagram shows the horizontal forces acting on a car travelling along a straight road.

(i) Calculate the size of the resultant force acting on the car.

Show clearly how you work out your answer.

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Resultant force = ......................................... N(2)

(ii) Describe the motion of the car when the forces shown in the diagram act on it.

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(b) A car driver makes an emergency stop.


(i) Calculate the total stopping distance of the car.

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Stopping distance = ................................. m(1)

(ii) The graph shows that speed affects thinking distance.

Use the graph to find the thinking distance for a car driven at 30 m/s.

Thinking distance = ................................ m(1)

(iii) Give one further factor that will affect the thinking distance.

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(Total 7 marks)

Q18. (a) The graphs show how the velocity of two cars, A and B, change from the moment the car drivers see an obstacle blocking the road.

Car A Car B

One of the car drivers has been drinking alcohol. The other driver is wide awake and alert.

(i) How does a comparison of the two graphs suggest that the driver of car B is the one who has been drinking alcohol?

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(ii) How do the graphs show that the two cars have the same deceleration?

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(1)

(iii) Use the graphs to calculate how much further car B travels before stopping compared to car A.


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Additional stopping distance = ............................................... m(3)

(b) In a crash test laboratory, scientists use sensors to measure the forces exerted in collisions. The graphs show how the electrical resistance of 3 experimental types of sensor, X, Y and Z, change with the force applied to the sensor.

Which of the sensors, X, Y or Z, would be the best one to use as a force sensor?

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(Total 7 marks)

Q19. (a) The total stopping distance of a car has two parts. One part is the distance the car travels during the driver’s reaction time. This distance is often called the ‘thinking distance’.

What distance is added to the ‘thinking distance’ to give the total stopping distance?

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(b) The graph shows the relationship between the speed of a car and the thinking distance.

Describe the relationship between speed and thinking distance.

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(c) The diagram shows two students investigating reaction time.

One student holds a 30 cm ruler, then lets go. As soon as the second student sees the ruler fall, she closes her hand, stopping the ruler. The further the ruler falls before being stopped, the slower her reaction time.

(i) One student always holds the ruler the same distance above the other student’s hand.In this experiment, what type of variable is this?

Put a tick ( ) in the box next to your answer.

independent variable

dependent variable

control variable

(1)

(ii) Describe how this experiment could be used to find out whether listening to music affects reaction time.

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(d) The following information is written on the label of some cough medicine.

WARNING: Causes drowsiness.Do not drive or operate machinery.

How is feeling drowsy (sleepy) likely to affect a driver’s reaction time?

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(e) Three cars, X, Y and Z , are being driven along a straight road towards a set of traffic lights.The graphs show how the velocity of each car changes once the driver sees that the traffic light has turned to red.

Which one of the cars, X, Y or Z , stops in the shortest distance?

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(Total 8 marks)

Q20. (a) The diagram shows three identical go-karts, P, Q and R, travelling at different speeds along the straight part of an outdoor racetrack.

Which go-kart, P, Q or R, has the greatest momentum?

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Give the reason for your answer.

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(b) The total mass of go-kart Q and the driver is 130 kg.

(i) Use the equation in the box to calculate the total momentum of go-kart Q and the driver.

momentum = mass × velocity


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Momentum = ...........................................(2)

(ii) Which of the following is the unit of momentum?

Draw a ring around your answer.

J/s kg m/s Nm

(1)

(c) To race safely at high speed, a go-kart driver must have fast reaction times and the outdoor racetrack should be dry.

(i) How would being tired affect a driver’s reaction time?

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(ii) How would a wet track affect the braking distance of a go-kart?

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(Total 7 marks)

Q21.The arrows in the diagram represent the horizontal forces acting on a motorbike at one moment in time.

(a) The mass of the motorbike and rider is 275 kg.

Use the equation in the box to calculate the acceleration of the motorbike at this moment in time.

resultant force = mass × acceleration


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Acceleration = ............................................................ m/s2

(3)

(b) A road safety organisation has investigated the causes of motorbike accidents.

The main aim of the investigation was to find out whether there was any evidence that young, inexperienced riders were more likely to be involved in an accident than older, experienced riders.

Data obtained by the organisation from a sample of 1800 police files involving motorbike accidents, is summarised in the table.

Size of motorbikeengine

Percentage of allmotorbikes sold

Total number inthe sample of

1800accident files

up to 125 cc 36 774

126 to 350 cc 7 126

351 to 500 cc 7 162

over 500 cc 50 738

Most of the motorbikes with engines up to 125 cc were ridden by young people.The motorbikes with engines over 500 cc were ridden by older, more experienced riders.

(i) In terms of the main aim of the investigation, is this data valid?

Draw a ring around your answer. NO YES

Explain the reason for your answer.

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(ii) The organisation concluded that:

“Young, inexperienced riders are more likely to be involved in a motorbike accident than older, experienced riders”.

Explain how the data supports this conclusion.

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(c) Of particular concern to motorbike riders is the design of steel crash barriers. Riders falling off and sliding at high speed into a steel support post are often seriously injured.

One way to reduce the risk of serious injury is to cover the post in a thick layer of high impact polyurethane foam.

(i) Use the ideas of momentum to explain how the layer of foam reduces the risk of serious injury to a motorbike rider sliding at high speed into the support post.

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(ii) Crash barrier tests use dummies that collide at 17 m/s with the barrier. Each test costs about £12 000. New safety devices for crash barriers are tested many times to make sure that they will improve safety.

Do you think that the cost of developing the new safety devices is justified?

Draw a ring around your answer. NO YES


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...............................................................................................................(1)

(Total 11 marks)

Q22. Motorway accidents have many causes.

(a) Which one of the following is most likely to increase the chance of a car being in an accident?

Tick ( ) the box next to your answer.

The car has just had new tyres fitted.

The driver has been drinking alcohol.

A road surface in dry conditions


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(b) The diagram shows three designs of motorway crash barriers.

Steel sheets Steel ‘ropes’ Solid concrete

Before a new design of barrier is used, it must be tested.A car of mass 1500 kg is driven at 30 m/s to hit the barrier at an angle of 20 degrees.This barrier must slow the car down and must not break.

Explain why the mass of the car, the speed of the car and the angle at which the car hits the barrier must be the same in every test.

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(c) A group of scientists has suggested that new designs of crash barriers should be first tested using computer simulations.

Which two statements give sensible reasons for testing new barrier designs using a computer simulation?

Put a tick ( ) in the box next to each of your answers.

The design of the barrier can be changed easily.

Data for different conditions can be obtained quickly.

Simulations are more realistic than using cars and barriers.

(1)(Total 5 marks)

Q23. (a) A car is being driven along a straight road. The diagrams, A, B and C, show the horizontal forces acting on the moving car at three different points along the road.

Describe the motion of the car at each of the points, A, B and C.

(3)

(b) The diagram below shows the stopping distance for a family car, in good condition, driven at 22 m/s on a dry road. The stopping distance has two parts.

(i) Complete the diagram below by adding an appropriate label to the second part of the stopping distance.

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.............................................................(1)

(ii) State one factor that changes both the first part and the second part of the stopping distance.

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(c) The front crumple zone of a car is tested at a road traffic laboratory. This is done by using a remote control device to drive the car into a strong barrier. Electronic sensors are attached to the dummy inside the car.

(i) At the point of collision, the car exerts a force of 5000 N on the barrier.

State the size and direction of the force exerted by the barrier on the car.

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...............................................................................................................(1)

(ii) Suggest why the dummy is fitted with electronic sensors.

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...............................................................................................................(1)

(iii) The graph shows how the velocity of the car changes during the test.

Use the graph to calculate the acceleration of the car just before the collision with the barrier.

Show clearly how you work out your answer, including how you use the graph, and give the unit.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Acceleration = ............................................................(3)

(Total 10 marks)

Q24.(a) The graphs show how the velocity of two cars, A and B, change from the moment the car drivers see an obstacle blocking the road.

Time in secondsTime in seconds

One of the car drivers has been drinking alcohol. The other driver is wide awake and alert.

(i) How does a comparison of the two graphs suggest that the driver of car B is the one who has been drinking alcohol?

...............................................................................................................

...............................................................................................................(1)

(ii) How do the graphs show that the two cars have the same deceleration?

...............................................................................................................

...............................................................................................................(1)

(iii) Use the graphs to calculate how much further car B travels before stopping compared to car A.


...............................................................................................................

...............................................................................................................

...............................................................................................................

Additional stopping distance = .................................................. m(3)

(b) In a crash-test laboratory, scientists use sensors to measure the forces exerted in collisions. The graphs show how the electrical resistance of 3 experimental types of sensor, X, Y, and Z, change with the force applied to the sensor.

Which of the sensors, X, Y or Z, would be the best one to use as a force sensor?

..................................................


........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 7 marks)

Q25.(a) A car driver makes an emergency stop.


Calculate the total stopping distance of the car.

.......................................................................................................................

Stopping distance = .................................................. m(1)

(b) The graph shows how the braking distance of a car driven on a dry road changes with the car’s speed.

Speed in m/s

The braking distance of the car on an icy road is longer than the braking distance of the car on a dry road.

(i) Draw a new line on the graph to show how the braking distance of the car on an icy road changes with speed.

(2)

(ii) Which one of the following would also increase the braking distance of the car?

Put a tick ( ) in the box next to your answer.

Rain on the road

The driver having drunk alcohol

The driver having taken drugs

(1)

(c) The thinking distance depends on the driver’s reaction time.

The table shows the reaction times of three people driving under different conditions.

Car driver Condition

Reaction time in second

A Wide awake with no distractions 0.7

B Using a hands-free mobile phone 0.9

C Very tired and listening to music 1.2

The graph lines show how the thinking distance for the three drivers, A, B, and C, depends on how fast they are driving the car.

Speed in m/s

(i) Match each graph line to the correct driver by writing A, B, or C in the box next to the correct line.

(2)

(ii) The information in the table cannot be used to tell if driver C’s reaction time is increased by being tired or by listening to music.Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 8 marks)

Q26.(a) Some students have designed and built an electric-powered go-kart. After testing, the students decided to make changes to the design of their go-kart.

The go-kart always had the same mass and used the same motor.

The change in shape from the first design (X) to the final design (Y) will affect the top speed of the go-kart.

Explain why.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(b) The final design go-kart, Y, is entered into a race.

The graph shows how the velocity of the go-kart changes during the first 40 seconds of the race.

Time in seconds

(i) Use the graph to calculate the acceleration of the go-kart between points J and K.

Give your answer to two significant figures.

...............................................................................................................

...............................................................................................................

...............................................................................................................

Acceleration = ........................................ m/s2

(2)

(ii) Use the graph to calculate the distance the go-kart travels between points J and K.

...............................................................................................................

...............................................................................................................

...............................................................................................................

Distance = ........................................ m(2)

(iii) What causes most of the resistive forces acting on the go-kart?

...............................................................................................................(1)

(Total 8 marks)

Q27.A car has an oil leak. Every 5 seconds an oil drop falls from the bottom of the car onto the road.

(a) What force causes the oil drop to fall towards the road?

........................................................................................................................(1)

(b) The diagram shows the spacing of the oil drops left on the road during part of a journey

Describe the motion of the car as it moves from A to B.

........................................................................................................................

Explain the reason for your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(c) When the brakes are applied, a braking force slows down and stops the car.

(i) The size of the braking force affects the braking distance of the car.

State one other factor that affects the braking distance of the car.

...............................................................................................................(1)

(ii) A braking force of 3 kN is used to slow down and stop the car in a distance of 25 m.

Calculate the work done by the brakes to stop the car and give the unit.

Use the correct equation from the Physics Equations Sheet.

...............................................................................................................

...............................................................................................................

...............................................................................................................

Work done =..................................................(3)

(Total 8 marks)

Q28.(a) The stopping distance of a vehicle is made up of two parts, the thinking distance and the braking distance.

(i) What is meant by thinking distance?

...............................................................................................................

...............................................................................................................(1)

(ii) State two factors that affect thinking distance.

1 ...............................................................................................................

...............................................................................................................

2 ...............................................................................................................

...............................................................................................................(2)

(b) A car is travelling at a speed of 20 m/s when the driver applies the brakes. The car decelerates at a constant rate and stops.

(i) The mass of the car and driver is 1600 kg.

Calculate the kinetic energy of the car and driver before the brakes are applied.


...............................................................................................................

...............................................................................................................

...............................................................................................................

Kinetic energy = .................................................. J(2)

(ii) How much work is done by the braking force to stop the car and driver?

Work done = .................................................. J(1)

(iii) The braking force used to stop the car and driver was 8000 N.

Calculate the braking distance of the car.


...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Braking distance = .................................................. m(2)

(iv) The braking distance of a car depends on the speed of the car and the braking force applied.

State one other factor that affects braking distance.

...............................................................................................................

...............................................................................................................(1)

(v) Applying the brakes of the car causes the temperature of the brakes to increase.

Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(c) Hybrid cars have an electric engine and a petrol engine. This type of car is often fitted with a regenerative braking system. A regenerative braking system not only slows a car down

but at the same time causes a generator to charge the car’s battery.

State and explain the benefit of a hybrid car being fitted with a regenerative braking system.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(Total 14 marks)

Q29.The diagram shows how the thinking distance and braking distance of a car add together to give the stopping distance of the car.

(a) Use words from the box to complete the sentence.

distance energy force time

The stopping distance is found by adding the distance the car travels during the

driver’s reaction ........................................ and the distance the car travels under the

braking ........................................ .(2)

(b) Which one of the following would not increase the thinking distance?

Tick ( ) one box.

The car driver being tired.

The car tyres being badly worn.

The car being driven faster.

(1)

(c) The graph shows how the braking distance of a car changes with the speed of the car.The force applied to the car brakes does not change.

Speed in metres/second

(i) What conclusion about braking distance can be made from the graph?

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(ii) The graph is for a car driven on a dry road.

Draw a line on the graph to show what is likely to happen to the braking distance at different speeds if the same car was driven on an icy road.

(1)

(d) A local council has reduced the speed limit from 30 miles per hour to 20 miles per hour on a few roads. The reason for reducing the speed limit was to reduce the number of accidents.

(i) A local newspaper reported that a councillor said:

“It will be much safer because drivers can react much faster when driving at 20 miles per hour than when driving at 30 miles per hour.”

This statement is wrong. Why?

...............................................................................................................

...............................................................................................................(1)

(ii) The local council must decide whether to introduce the lower speed limit on a lot more roads.

What evidence should the local council collect to help make this decision?

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 9 marks)

Q30.(a) The diagram shows a car at position X.

The handbrake is released and the car rolls down the slope to Y.The car continues to roll along a horizontal surface before stopping at Z.The brakes have not been used during this time.

(i) What type of energy does the car have at X?

................................................................................(1)

(ii) What type of energy does the car have at Y?

................................................................................(1)

(b) The graph shows how the velocity of the car changes with time between Y and Z.

(i) Which feature of the graph represents the negative acceleration between Y and Z?

................................................................................................................(1)

(ii) Which feature of the graph represents the distance travelled between Y and Z?

................................................................................................................(1)

(iii) The car starts again at position X and rolls down the slope as before.This time the brakes are applied lightly at Y until the car stops.

Draw on the graph another straight line to show the motion of the car between Y andZ.

(2)

(c) Three students carry out an investigation. The students put trolley D at position P on a slope. They release the trolley. The trolley rolls down the slope and along the floor as shown in the diagram.

The students measure the distance from R at the bottom of the slope to S where the trolley stops. They also measure the time taken for the trolley to travel the distance RS.They repeat the investigation with another trolley, E.

Their results are shown in the table.

Trolley Distance RS incentimetres

Time taken inseconds

Average velocityin

centimetresper second

D 65 2.1

E 80 2.6

(i) Calculate the average velocity, in centimetres per second, between R and S for trolleys D and E. Write your answers in the table.

Use the correct equation from Section A of the Physics Equations Sheet.

................................................................................................................

................................................................................................................

................................................................................................................(3)

(ii) Before the investigation, each student made a prediction.

• Student 1 predicted that the two trolleys would travel the same distance.

• Student 2 predicted that the average velocity of the two trolleys would be the same.

• Student 3 predicted that the negative acceleration of the two trolleys would be the same.

Is each prediction correct?

Justify your answers.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................(3)

(Total 12 marks)

Q31.An investigation was carried out to show how thinking distance, braking distance and stopping distance are affected by the speed of a car.

The results are shown in the table.

Speedin

metresper second

Thinkingdistancein metres

Brakingdistance inmetres

Stoppingdistancein metres

10 6 6 12

15 9 14 43

20 12 24 36

25 15 38 53

30 18 55 73

(a) Draw a ring around the correct answer to complete each sentence.

As speed increases, thinking distance

decreases.

increases.

stays the same.

As speed increases, braking distance

decreases.

increases.

stays the same.

(2)

(b) One of the values of stopping distance is incorrect.

Draw a ring around the incorrect value in the table.

Calculate the correct value of this stopping distance.

.........................................................................................................................

Stopping distance = ................................ m(2)

(c) (i) Using the results from the table, plot a graph of braking distance against speed.

Draw a line of best fit through your points.

Speed in metres per second(3)

(ii) Use your graph to determine the braking distance, in metres, at a speed of 22 m / s.

Braking distance = ................................ m(1)

(d) The speed–time graph for a car is shown below.

While travelling at a speed of 35 m / s, the driver sees an obstacle in the road at time t = 0. The driver reacts and brakes to a stop.

Time in seconds

(i) Determine the braking distance.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

Braking distance = ................................ m(3)

(ii) If the driver was driving at 35 m / s on an icy road, the speed–time graph would be different.

Add another line to the speed–time graph above to show the effect of travelling at 35 m / s on an icy road and reacting to an obstacle in the road at time t = 0.

(3)

(e) A car of mass 1200 kg is travelling with a velocity of 35 m / s.

(i) Calculate the momentum of the car.


Give the unit.

................................................................................................................

................................................................................................................

................................................................................................................

Momentum = ..........................................(3)

(ii) The car stops in 4 seconds.

Calculate the average braking force acting on the car during the 4 seconds.


................................................................................................................

................................................................................................................

Force = ................................ N(2)

(Total 19 marks)

M1. (a) evidence of distance = speed × time or 4 × 20gains 1 mark

but80

gains 2 marks

units mfor 1 mark

3

(b) idea that (both) become warm/hotfor 1 mark

idea of wearing (away/down)/becoming scratchedgains 1 mark

but(brake) pads wear more (than wheel discs)

gains 2 marks3

[6]

M2. (a) Any three factors from any of the

groups of factors below (1) each a clear and correct statement of theeffect of the particular factor on the stopping distance (1) each

do not credit mobile phones do not credit other distractions2

examples: (factors relating to the driver)* (driver’s) reaction time or time for the driver to apply the brakesthe longer the reaction time the longer the s.d.

which may be related to age, experience, sobriety, effect of drugs, mental capacity, physical capacity, driver fatigue, confusion and panicdoes not depend on the driver’s eyesight as this affects the occurrence of the ‘need-to-stop’ realisation rather than the stopping distance

examples: (factors relating to the car)4

* force applied by the brakes the greater the force the shorter the s.d.* speed (of the car) the greater the speed the longer the s.d.* mass or weight (of the car) the greater the mass or weight the longer the s.d.* ABS answers

examples: (factors relating to the road or tyres)

* tread on the tyres or friction the more tread or friction the shorter the s.d.* slipperiness of the road the greater the slipperiness the longer the s.d.* it is raining

does not depend on the visibility as this affects the occurance of the ‘need-to-stop’ realisation rather than the stopping distance

(b) velocityaccept speed

1

massaccept weight or shape or aerodynamicsdo not credit size

1

(c) any two ((1) + (1)) each ofdo not credit a description

* friction (between the tyres and the road) backwards or opposite to the direction of motiondo not credit the direction if the force not specified

* air resistance or drag or wind resistance backwards or opposite to the direction of motion

do not credit wind

* weight or gravity down (wards) or towards the centre of the Earthdo not credit mass or inertia

* reaction (of or from the road) upwards4

(d) directionallow bearing(s)do not credit orientation

1[13]

M3. (a) (i) the pushing force balanced by the frictionaccept the pushing force equals friction or pushing force is too small or frictional force is too great

1

(ii) any two from

an unbalanced force acts on the model bus

the model bus moves

in same direction as pushing forceaccept forwards

and will speed up2

(iii) force (applied)any order

1

distance ( moved)1

(b) (i) car is travelling fast1

driver has been drinking alcohol1

ice on the road1

(ii) tyres and road / ground1

[9]

M4. (a) (i) E-F (ticked)1

(ii) B-C or D-Eaccept both answers

1

(b) fast(er)accept downhill

1

slow(er)1

forcedo not accept distance

1[5]

M5. (a) time1

force1

(b) any three from

• driver’s reactions are slow(er)accept driver could have taken drugsor alcohol or due to tiredness ordistractions

• poor weather conditionsaccept raining or snowing or fog /mist (poor visibility)

• greater mass or weight• poor road conditions

oil / gravel / mud / leaves / wet / icygoing downhill

• poorly maintained brakesdo not accept driver’s weak foot force

• worn tyres3

[5]

M6. (a) WX deceleration / speed decreasing / slowing down / negative acceleration

XY constant speed / steady speed not constant motion / slow speed

YZ acceleration / speed increasing / speeding upfor 1 mark each

3

(b) distance = v × t or distance = 30 × 20gains 1 mark

butdistance = 600(m)

gains 2 marks2

(c) acceleration = v / t or acceleration = 30 / 12gains 1 mark(if –30 / 12, allow negative sign here if not in the answer)

3

but

acceleration = 2.5 (m/s²)gains 2 marks

butacceleration = -2.5 (m/s²)

gains 3 marks

(d) in a crash / during hard braking car body stops / slows rapidly driver / passengers continue to move forward not thrown forward seatbelts provide backward force / keep them in their seats / restrain them to stop them hitting the windscreen / dashboard

(an alternative argument involving momentum is acceptable) for 1 mark each

4[12]

M7. (a) (i) tiredness / boredomdrugsalcoholdistraction

any two for 1 mark each2

(ii) A greater / longerB no effectC greater / longer

each for 1 mark3

(b) on a wet road: there is less friction / gripfor 1 mark

braking distance is greater / takes longer to stopor car skids / slides forwardfor 1 mark

2

(c) (i) deceleration = gradient or 30 / 4.8each for 1 mark

2

(ii) force = mass × acceleration or 900 × 6.25each for 1 mark

2

(iii) distance = area under graph or 0.5 × 4.8 × 30 or averagespeed × time or 15 × 4.8Accept answer in terms of change in k.e. = work doneif incorrect unit given (eg 72km) then no mark

each for 1 mark2

[13]

M8. (a) ABfor 1 mark

1

(b) (i) 0.7for 1 mark each

1

(ii) 16.8gains 2 marks

2

but correct working(d = v.t, d = 24 × 0.7, or in terms of area under graph)

gains 1 mark1

(c) a = (v-u)/t= 24/4= 6m/s2

(see marking of calculations)

(can work in terms of graph gradient)4

(d) d = v.t= 24/2 × 4= 48(see marking of calculations)

(can work in terms of area under graph)3

(e) F = ma= 800 × 6= 4800

(see marking of calculations)3

[15]

M9. (a) Each scale optimum

Else both half sizeStraight line joining 30,0 to 30,0.67 to 0, 5.67

any 5 for 1 mark each5

(b) 6Else a = 30/5

gets 2 marks

Else a = v/tgets 1 mark

3

(c) 9000Else F = 6 × 1500

gets 2 marks

Else F = magets 1 mark

3

(d) (i) Driver has forward momentumWhich is conservedGiving drive relative forward speed to car

for one mark each3

(ii) If inelastic ke lostHere ke does work crumpling car

for 1 mark each2

(iii) Car stops in 75mgets 1 mark

W = F.d or 9000 × 75gets 1 mark

W = 675 000 JOR ke = 1/2 mv2

gets 1 mark

ke = 1/2.1500.302ke = 675 000 J3

[19]

M10. (a) points correct; line correctfor 1 mark each

2

(b) increasesfor 1 mark

1

(c) (i) 9for 1 mark

1

(ii) 6 ecffor 1 mark

1

(iii) increased ecffor 1 mark

1[6]

M11. (a) (i) gravity/weight1

(ii) 2193750000000 or 2.19 × 1012

not 2.1912

allow 1 mark for the correct conversion to 7500 (m/s)allow one mark for answer 2193750(J)

2

transferred to heatignore extras of sound and lightaccept changed to heataccept lost due to friction

1

(b) (i) acceleration =

accept word speed instead of velocity

accept a =

or correct rearrangementdo not accept

even if subsequent calculation correct

can gain credit if subsequent calculation correct1

(ii) 2ignore + or – signs

m/s2 1accept m/s/s or ms2

2

(c) (i) force = mass × accelerationaccept correct rearrangementaccept F = m × ado not accept

unless subsequent calculation correct1

(ii) 156 000accept 78 000 × their (b)(ii)(only if (b)(i) correct)

1[9]

M12. (a) (i) constant speeddo not accept normal speeddo not accept it is stopped / stationary

1

in a straight lineaccept any appropriate reference to a directionconstant velocity gains 2 marks‘not accelerating’ gains 2 marks

terminal velocity alone gets 1 mark1

(ii) goes down owtteaccept motorbike (it) slows down

1

(b) (i) 20 (m/s)ignore incorrect units

1

(ii) acceleration =

do not accept velocity for change in velocityaccept change in speed

accept or

or a =

do not accept 1

(iii) 4

or their (b)(i) ÷ 5allow 1 mark for correct substitution

2

m/s2

m/s/s or ms or metres persecond squared or metres persecond per second

1

(c) vehicle may skid / slideloss of control / brakes lock / wheels lockaccept greater stopping distance or difficult to stop

1

due to reduced friction (between tyre(s) and road)accept due to less gripdo not accept no friction

1

(d) any three from:do not accept night time / poor vision

• increased speed

• reduced braking force

• slower (driver) reactionsNB specific answers may each gain credit eg tiredness (1), drinking alcohol (1), using drugs (1), driver distracted (1) etc

• poor vehicle maintenancespecific examples may each gain credit eg worn brakes or worn tyres etc

• increased mass / weight of vehicleaccept large mass / weight of vehicle

• poor road surface

• more streamlinedif candidates give three answers that affect stopping distance but not specific to increase award 1 mark only

3[13]

M13. (a) MNaccept 5.8, 8 seconds must include unit

1

(b) LMaccept 0.8, 5.8 seconds must include unit

1

(c) (i) 0.81

(ii) drinking alcohol1

(d) straight (by eye) line starting at 0.8 seconds1

line drawn steeper than LM starting before Lignore lines going beyond 2 seconds but line must exceed 2.5 metres per second before terminating

1[6]

M14. (a) (i) as one goes up so does the other

or (directly) proportionalaccept change by the same ratio

1

(ii) steeper straight line through the originjudge by eye

1

(iii) Yes with reason

eg data would have been checked / repeatedaccept produced by a reliable/ official/ government sourcedo not accept it needs to be reliable

or No with reason

eg does not apply to all conditions / cars / drivers

or are only average values

or Maybe with a suitable reason

eg cannot tell due to insufficient information1

(b) (i) stopping distance = thinking distance + braking distance1

(ii) any two from:factors must be to do with increasing braking distance

• smooth road / loose surface

• rain / snow / iceaccept wet road/ petrol spillsdo not accept condition of road unless suitably qualified

• badly maintained brakesaccept worn brakesaccept bad/ worn/ rusty brakesdo not accept old brakes

• worn tyresaccept bald tyresaccept lack of grip on tyresdo not accept old tyres

• downhill slope/gradient

• heavily loaded car2

[6]

M15. (a) 53 (m)1

(b) (i) Similar shape curve drawn above existing line going through (0, 0)allow 1 mark for any upward smooth curve or straight upward line above existing line going through (0, 0)

2

(ii) rain on road1

car brakes in bad condition1

(c) (i) all three lines correctly labelledallow 1 mark for one correctly labelled

top line – Caccept 1.2

middle line – Baccept 0.9

bottom line – Aaccept 0.7

2

(ii) any two from:

• (table has) both variables are togetheraccept tired and music as named variables

• both (variables) could/ would affect the reaction time

• cannot tell original contributionaccept cannot tell which variable is affecting the drive (the most)

• need to measure one (variable) on its ownaccept need to test each separately

• need to control one of the variables2

[9]

M16. (a) (i) constant

1

(ii) heat1

(b) (i) 3 links correct

allow 1 mark for 1 correct linkif more than one line is drawn from a condition mark all lines from that condition incorrect

2

(ii) increased1

[5]

M17. (a) (i) 1500allow 1 mark for subtraction shown ie 2000 – 500

2

(ii) it accelerates1

in a forward directionaccept gains speed/velocity

1

(b) (i) 23 (m)1

(ii) 20 (m)only this answer

1

(iii) any one from:

• drinking alcohol

• taking drugs

• tiredaccept (a specific) distractionaccept any factor that affects the drivers reactions

1[7]

M18. (a) (i) longer reaction timeaccept slower reactionsdo not accept slower reaction time unless qualified

orgreater thinking distance

accept greater thinking timeorgreater stopping distance

accept greater stopping timegreater braking distance negates answer

1

(ii) lines / slopes have the same gradientaccept slopes are the same

orvelocity decreases to zero in same time / in 2.6 seconds

accept any time between 2.3 and 2.8accept braking distances are the same

1

(iii) 12accept extracting both reaction times correctly for 1 mark(0.6 and 1.4 ) or time = 0.8(s) for 1 markaccept 0.8 × 15 for 2 marksaccept calculating the distancetravelled by car A as 28.5 m or the distance travelled by car B as 40.5 m for 2 marks

3

(b) Z1

different force values give a unique / different resistanceonly scores if Z chosendo not accept force andresistance are (directly) proportionalaccept answers in terms of whyeither X or Y would not be the best eg

X – same resistance value is obtained for 2 different force valuesY – all force values give the same resistance

1[7]

M19. (a) distance travelled under the braking forceaccept braking (distance)

1

(b) (directly) proportionalaccept a correct description using figures

orincrease in the same ratio

eg if speed doubles thenthinking distance doublesaccept for 1 mark positive correlationaccept for 1 mark as speedincreases so does thinking distanceaccept as one increases the other increasesaccept as thinking distance increases speed increases

2

(c) (i) control variable1

(ii) experiment done, student listens to music / ipod (etc)1

experiment (repeated), student not listening to musicfor both marks to be awarded there must be a comparison

1

(d) increase itaccept an answer which implies reactions are slowerdo not accept answers in terms of thinking distance only

1

(e) Y1

[8]

M20. (a) Rreason cannot score if R is not chosen

1

has the greatest speed / velocityaccept it is going at 28 m/sanswer should be comparative

1

(b) (i) 3250allow 1 mark for correct substitution of 130 and 25ie 130 × 25accept 2600 or 3640 for 1 mark

2

(ii) kg m/saccept answer given in (b)(i) if no answer given here

1

(c) (i) increase itaccept make it sloweraccept slow it downaccept make it longeraccept (reactions) would be slowerdo not accept if the answer clearly refers to distancecomparative answers expected

1

(ii) increase itaccept make it longerdo not accept if the answer clearly refers to timecomparative answers expected

1[7]

M21. (a) 4.22 marks for correct substitution and transformation, ie 1155/275allow 1 mark for correct resultant force with a subsequent incorrect method, ie 1155allow 1 mark for an incorrect resultant force with a subsequent correct method,eg answers of 7.27 or 10.34 gain 1 mark

3

(b) (i) YESmarks are for the explanation

any two from:

• data (from police files) can be trusted

• data answers the question askedallow a conclusion can be made from the data

• large sample used

NO

any two from:

• the sample is not representative

• the sample size is too small

• accident files do not indicate age / experience of ridersan answer YES and NO can score 1 mark from each set of mark points

2

(ii) more accidents with motorbikes up to 125 ccaccept for 2 marks an answer in terms of number of under 125 cc to accidents ratio compared correctly with number of over 500 cc to accidents ratio

1

even though there are fewer of these bikes than bikes over 500 cc1

(c) (i) increases the time taken to stopaccept increases collision time

1

decreases rate of change in momentumaccept reduces acceleration / deceleration

accept reduces momentum is insufficient

1

reduces the force (on the rider)1

(ii) YES

any sensible reason, eg:the mark is for the reason

• cannot put a price on life / injuryaccept may save lives

• fewer (serious) injuriesaccept reduces risk of injury

• reduces cost of health care / compensation

NO

any sensible suggestion, eg:

• money better spent on …needs to be specific

• total number of riders involved is small1

[11]

M22. (a) The driver has been drinking alcohol.reason only scores if this box is ticked

1

driver's reaction time increasesaccept slower reactionsaccept slower reaction time

orthinking distance / stopping distance increases

do not accept braking distance increasesordriver less alert

accept driver may fall asleep / be tired1

(b) they are all variables that could affect outcome / resultsaccept specific effect of changing one of the variablesaccept to make the test validignore reliable

1

so data / barriers can be comparedaccept to see which is / works best / safestdo not accept fair test on its own

1

(c) ticks in both the top and middle boxes1

[5]

M23. (a) A constant speed / velocity

accept steady pacedo not accept terminal velocitydo not accept stationary

1

B accelerationaccept speeding up

1

C decelerationaccept slowing downaccept accelerating backwardsaccept accelerating in reversedo not accept decelerating backwards

1

(b) (i) the distance the car travels under the braking forceaccept braking distance

1

(ii) speed/velocity/momentum1

(c) (i) 5000 (N) to the leftboth requiredaccept 5000(N) with the direction indicated by an arrow drawn pointing to the leftaccept 5000(N) in the opposite direction to the force of the car (on the barrier)accept 5000(N) towards the car

1

(ii) to measure/detect forces exerted (on dummy / driver during the collision)1

(iii) 4allow 1 mark for showing a triangle drawn on the straight part of the graphor correct use of two pairs of coordinates

2

m/s2

do not accept mps2

1[10]

M24.(a) (i) longer reaction timeaccept slower reactions

do not accept slower reaction time unless qualified

orgreater thinking distance

accept greater thinking time

orgreater stopping distance

accept greater stopping timegreater braking distance negates answer

1

(ii) lines / slopes have the same gradientaccept slopes are the same

orvelocity decreases to zero in same time / in 2.6 seconds

accept any time between 2.4 and 2.8accept braking distances are the same

1

(iii) 12accept extracting both reaction times correctly for 1 mark(0.6 and 1.4)or time = 0.8 (s) for 1 markaccept 0.8 × 15 for 2 marksaccept calculating the distance travelled by car A as 28.5 morthe distance travelled by car B as 40.5 m for 2 marks

3

(b) Z1

different force values give a unique / different resistanceonly scores if Z chosendo not accept force and resistance are (directly) proportionalaccept answers in terms of why either X or Y would not be best egX – same resistance value is obtained for 2 different force valuesY – all force values give the same resistance

1[7]

M25.(a) 96 (m)1

(b) (i) similar shape curve drawn above existing line going through (0,0)allow 1 mark for any upward smooth curve or straight upward lineabove existing line going through (0,0)

2

(ii) Rain on the road1

(c) (i) all three lines correctly labelledallow 1 mark for one correctly labelled

top line – Caccept 1.2

middle line – Baccept 0.9

bottom line – Aaccept 0.7

2

(ii) any two from:

• (table has) both variables are togetheraccept tired and music as named variables

• both (variables) could / would affect the reaction timeaccept cannot tell which variable is affecting the drive (the most)

• cannot tell original contribution

• need to measure one (variable) on its ownaccept need to test each separately

• need to control one of the variablesfair test is insufficient

2[8]

M26.(a) more streamlinedaccept decrease surface area

1

air resistance is smaller (for same speed)accept drag for air resistancefriction is insufficient

1

so reaches a higher speed (before resultant force is 0)ignore reference to mass

1

(b) (i) 1.7

allow 1 mark for correct method, ie or allow 1 mark for an answer with more than 2 sig figs that rounds to 1.7

or allow 1 mark for an answer of 172

(ii) 7.5

allow 1 mark for correct use of graph, eg × 5 × 32

(iii) air (resistance)accept wind (resistance)drag is insufficientfriction is insufficient

1[8]

M27.(a) gravitational / gravity / weightdo not accept gravitational potential

1

(b) acceleratingaccept speed / velocity increases

1

the distance between the drops increases1

but the time between the drops is the sameaccept the time between drops is (always) 5 seconds accept the drops fall at the same rate

1

(c) (i) any one from:

• speed / velocity

• (condition of) brakes / road surface / tyres

• weather (conditions)accept specific examples, eg wet / icy roadsaccept mass / weight of car friction is insufficientreference to any factor affecting thinking distance negates this answer

1

(ii) 75 000allow 1 mark for correct substitution, ie 3000 × 25 provided no subsequent step shownor allow 1 mark for an answer 75or allow 2 marks for 75 k(+ incorrect unit), eg 75 kN

2

joules / J

do not accept jan answer 75 kJ gains 3 marksfor full marks the unit and numerical answer must be consistent

1[8]

M28.(a) (i) distance vehicle travels during driver’s reaction timeaccept distance vehicle travels while driver reacts

1

(ii) any two from:

• tiredness

• (drinking) alcohol

• (taking) drugs

• speed

• ageaccept as an alternative factor distractions, eg using a mobile phone

2

(b) (i) 320 000

allow 1 mark for correct substitution, ie × 1600 × 202 provided no subsequent step shown

2

(ii) 320000 or their (b)(i)1

(iii) 40

or

correctly calculatedallow 1 mark for statement work done = KE lostorallow 1 mark for correct substitution, ie 8000 × distance = 320 000 or their (b)(ii)

2

(iv) any one from:

• icy / wet roadsaccept weather conditions

• (worn) tyres

• road surface

• mass (of car and passengers)accept number of passengers

• (efficiency / condition of the) brakes1

(v) (work done by) friction (between brakes and wheel)

do not accept friction between road and tyres / wheels1

(causes) decrease in KE and increase in thermal energyaccept heat for thermal energy acceptKE transferred to thermal energy

1

(c) the battery needs recharging less oftenaccept car for battery

1

orincreases the range of the car

accept less demand for other fuels or lower emissions or lower fuel costs environmentally friendly is insufficient

as the efficiency of the car is increasedaccept it is energy efficient

1

the decrease in (kinetic) energy / work done charges the battery (up)accept because not all work done / (kinetic) energy is wasted

1[14]

M29.(a) timecorrect order only

1

force1

(b) The car tyres being badly worn1

(c) (i) braking distance increases with speedaccept positive correlationdo not accept stopping distance for braking distance

1

relevant further details, eg

• but not in direct proportion

• and increases more rapidly after 15 m/saccept any speed between 10 and 20accept numerical example

• double the speed, braking distance increases × 41

(ii) line drawn above existing line starting at the originas speed increases braking distance must increase each speed must have a single braking distance

1

(d) (i) reaction time / reaction (of driver) does not depend on speed (of car)1

(ii) (on the reduced speed limit roads) over the same period of timeaccept a specific time, eg 1 year

1

monitor number of accidents before and after (speed limit reduced)allow 1 mark only for record number of vehicles / cars using the (20 mph) roads or collect data on accidents on the (20 mph) roadsto score both marks the answer must refer to the roads with the reduced speed limit

1[9]

M30.(a) (i) gravitational potential (energy)1

(ii) kinetic (energy)1

(b) (i) slope or gradient1

(ii) area (under graph)do not accept region

1

(iii) starts at same y−intercept1

steeper slope than original and cuts time axis before originalthe entire line must be below the given lineallow curve

1

(c) (i) 31

and31

correct answers to 2 significant figures gains 3 marks even if no working shownboth values to more than 2 significant figures gains 2 marks:30.952…...30.769….65 / 2.1 and / or80 / 2.6 gains 1 markif incorrect answers given but if both are to 2 significant figures allow 1 mark

3

(ii) student 1 incorrect because 80 ≠ 651

student 2 correct because average velocities similarecf from (c)(i)

1

student 3 incorrect because times are different1

[12]

M31.(a) increases1

increases1

(b) 23 (m)accept 43 circled for 1 markaccept 9 + 14 for 1 mark

2

(c) (i) all points correctly plottedall to ± ½ small squareone error = 1 marktwo or more errors = 0 marks

2

line of best fit1

(ii) correct value from their graph (± ½ small square)1

(d) (i) 70½ × 35 × 4 gains 2 marksattempt to estimate area under the graph for 1 mark

3

(ii) line from (0.6,35)1

sloping downwards with a less steep line than the first line1

cutting time axis at time > 4.6 saccept cutting x-axis at 6

1

(e) (i) 42 0001200 × 35 gains 1 mark

2

kgm / sNs

1

(ii) 10 500 (N)42 000 / 4 gains 1 markalternatively:a = 35 / 4 = 8.75 m / s2

F = 1200 × 8.752

[19]

E1. Paper 1 Option P

In part (b), candidates often concentrated on how the car was stopped rather than on the heating and wearing of the pads and discs. Comparison of the effects on the two parts achieved good marks.

Paper 3 Option Q

In part (a) many candidates calculated the distance as 80 metres. Some candidates gave the units as m/s. A few candidates divided the speed by the time.

In (b) the majority of candidates recognised that heat was produced and that the pads wore down. Only the stronger candidates noted that the pads wore down faster than the discs.

E2. Many candidates could quote three relevant factors but then failed to state the effects they would have on the thinking, braking or stopping distance. Several weaker candidates appeared not to have read all the question. They used the three spaces to attempt descriptions of what they thought was meant by these distances. Many candidates knew acceleration as the rate of change of velocity or speed and that it depends on mass or weight. They could also identify gravity and its direction. Some candidates mentioned friction and air resistance. In describing the

direction of the force, many candidates were unclear, giving responses such as ‘towards the car’. Only a few of the better candidates recognised the vector nature of velocity.

E3. (a) Very few candidates expressed the idea of balanced forces, although the majority were able to state that the bus would move. Some went on to correctly indicate the direction in which the bus would move, or that it would speed up. The idea of unbalanced forces was rarely mentioned, with many candidates making imprecise statements about changes in the force of friction. The formula was usually correct, with ‘time taken’ or ‘speed’ being the most popular incorrect terms. Factors affecting stopping distances were well understood.

(b) Several candidates in (ii), did not appreciate that the friction is between the car’s tyres and the road.

E4. (a) This was well answered by most candidates. Very few failed to identify the steeper gradient of E-F but several weaker candidates ticked three boxes. Almost all successfully identified points between which the car was stationary.

(b) The most common error was to give ‘distance’ instead of ‘force’ to complete the last sentence.

E5. (a) The most common error was to give ‘distance’ instead of ‘force’ as the second word.

(b) Many candidates did not get full credit because they did not give a reason why the factor made the stopping distance greater; for example, ‘road surface’ should have stated ‘wet road surface’ or other acceptable reasons why the stopping distance would be greater. Sometimes candidates also gave several responses for the same mark, for example, the driver’s reactions are slower included taking of drugs, drinking alcohol, tiredness, distracted by using a mobile telephone or children in the car.

E6. The majority of candidates answered (a) correctly, though some weaker candidates though that the oil drops becoming closer together corresponded to acceleration and vice versa.

In part (b) the calculation of distance was mostly correct, but some candidates gave

30 × 20 = 60.

In part (c) the minus sign was often missing and a few candidates multiplied speed by time.

Most candidates were able to gain three marks for part (d). Only the most able candidates made it clear that, on sudden braking, the occupants of the car would continue to move forward, rather than being propelled forward.

E8. The question was very well answered. Almost all the candidates read the reaction time correctly from the graph and the vast majority then successfully calculated the distance travelled in this time. In part (c) a pleasingly high number of candidates completed the calculation for four marks, the unit for acceleration being somewhat better known than in previous years. In (d) the calculation proved to be more difficult although a large number of candidates did manage to produce a correct solution. An appreciable number of candidates used the area under the graph to correctly solve the problem, although a number complicated the situation by attempting to find the area using trapeziums and hence introduced inaccuracies. Although this technique is not on the syllabus it is correct and was given full credit. Of those candidates who failed to produce a correct answer the problem lay in not recognising that the average speed of the car during braking was 24/2 i.e. 12m/s. Part (e) was successfully completed by almost all of the candidates.

E10. The graph in part (a) was well drawn and parts (b) and (c) produced many fully correct answers. The main mistakes in (b) and (c)(iii) being replies in terms of time rather than distance. The error in the graphical axes did not appear to disadvantage candidates

E11. This question was well answered. However, it was disappointing that a substantial minority of candidates could not recall the equations correctly or complete a calculation without error even when they had written the equation. A common error in part (a)(ii) was to leave the speed in km/s rather than converting to mis. Most candidates had the right idea in part (a)(iii), but not all were specific enough to gain credit. In part (b)(ii) many candidates were able to work out the deceleration For those that did not, a common error was to use the orbital speed in the calculation. A number of candidates either omitted, or did not know, the correct unit for acceleration. In part (c)(ii) most candidates who had previously calculated the correct deceleration went on to calculate the correct force. A number of candidates failed to make the link between parts (b) and (c) and in the absence of any stated value for acceleration chose to use 10 m/s2.

E12. Although in part (a) the stem of the question clearly stated that the motorbike was moving, and the artwork reinforced this image of movement, many candidates incorrectly stated that the motorbike would be stationary. This was often followed by a statement that the motorbike would go backwards. In part (b) few candidates were able to recall the equation for acceleration or the correct unit. There were very few correct calculations. In part (c) most candidates were able to describe and explain what would happen to a car braking on an icy road and also give factors that could cause stopping distance to increase. However a number of candidates used imprecise language which meant that answers could not gain credit.

E13. Candidates were generally happy to use the letters in bold on the graph to identify different stages in the car’s journey. Where candidates supplied graph co-ordinates, many produced numerical values without stating the axis used.

(c) Most candidates achieved a least partial success.

(d) Many candidates did not offer responses to this part of the question. Those that did showed a widespread lack of understanding that the angle of slope of the line that they drew should be directly related to the greater initial acceleration of the cyclist.

E14. (a) (i) Most candidates gained a mark in correctly stating that the thinking distance is directly proportional to the speed.

(ii) Most candidates drew a correct line, although some drew the line parallel to the given line and above rather than going through the origin.

(iii) Answers to this question were varied. A number of candidates did not seem to know what the Highway Code was. Many of those who knew its origin and purpose thought that the numbers would have been exaggerated to encourage drivers to keep greater distances between cars.

(b) (i) This question was poorly answered with less than half the candidates gaining credit.

(ii) Many candidates did not read the question carefully and gave factors that would affect reaction time or gave speed as a factor.

E15. (a) Most candidates were aware that the stopping distance of 53 metres could be found

by adding the thinking distance and the braking distance. However, a significant number of responses were noted where the candidates had multiplied the figures together, producing a stopping distance of 570 metres. Candidates with this answer did not seem to appreciate that this was an unrealistic value.

(b) (i) There were some excellent attempts at good quality curves. However, significant numbers of candidates were careless, did not start at (0, 0) and many had lines below the original curve, or cutting through it.

(ii) The majority of candidates scored both marks with few candidates unable to score at least one mark.

(c) (i) The vast majority of candidates were able to correctly match the conditions to the graph lines.

(ii) Many candidates achieved credit by identifying that the data for Driver C was derived from the adverse effects of two conditions and that further tests would be required to determine the relative effects of either condition to the driver’s reaction time.

E16. (a)(i) and (a)(ii) The majority of candidates gave the correct answers.

(b)(i) Most candidates scored at least one mark, with a large proportion of candidates correctly linking the three conditions with the charts.

(b)(ii) There were many correct answers but a significant number of candidates gave an answer which could be interpreted in terms of time rather than distance.

Candidates should be encouraged to state the subject of the question first to reduce the possibility of any ambiguity, i.e. ‘The braking distance would be ….’.

E18. (a) (i) While many candidates answered this well, many let themselves down by a poor choice of language or ambiguous statements such as ‘the driver took longer to brake’ which could mean that the braking action occurred over a longer time or that the driver took longer to apply the brakes. Incorrect use of technical terms negated some otherwise correct answers. A minority of candidates also confused the time to see the incident with the time to react to the incident.

(ii) About three quarters of candidates gained this mark. Again a lack of precision in responses led to ambiguity which lost the mark: mentioning deceleration without specifying that velocity reached zero, stating that they both started from 15 m/s without saying they stopped, and vague statements that the ‘lines were the same’ without quoting gradient, slope or angle. Some candidates demonstrated an inability

to take times from the graph with wildly inaccurate values quoted from 1.2 s to ‘nearly 30 s’.

(iii) Few candidates recognised that they only needed to calculate the distance car B travelled in the extra thinking time part of the graph [(1.4-0.6)×15]. The majority of candidates knew that the area under the graph represents the distance travelled and gained marks accordingly. However, calculating these for both cars proved difficult due to the number of calculations involved and errors in obtaining the correct times from the graph. Many candidates did obtain two marks for completing only one of these calculations correctly. About two fifths of candidates failed to gain any marks.

(b) Some very good answers scored two marks but these were from less than a tenth of the candidates and were usually gained for explaining why X and/or Y were not suitable, rather than why Z is suitable. Most candidates scored one mark for correctly choosing Z but failed to give an acceptable reason. Many candidates clearly did not understand what a sensor was, describing it as a safety device that helped protect people in collisions by counteracting the forces they experienced rather than a device for measuring forces. Some candidates believed the resistance was some sort of resistance to collision, rather than electrical resistance, and made comments such as ‘Z would be better as impact time would be increased’ or ‘the increased resistance would reduce the effect of the collision’.

E19. (a) Surprisingly, only just over half of the candidates scored this mark. The most common errors being references to the time taken to come to a stop, or to the speed of the car.

(b) About two thirds of candidates correctly identified that an increase in speed produced an increase in thinking distance. A small proportion of candidates incorrectly referred to thinking time instead of distance. It was rare for candidates to go further and give a measure of how much the thinking distance would go up for a particular increase in speed. The alternative statement of direct proportionality was extremely rare.

(c) (i) Just under two thirds of candidates scored this mark.

(ii) Many candidates commented on why music would affect reaction time, giving reasons for both increasing and decreasing the reaction time. Those candidates who attempted to answer the question usually explained they would try the experiment with music playing but often forgot to repeat the experiment without music or say the results would need to be compared.

Many of the candidates who received no reward for this part question described experiments where the volume or genre of the music had become the independent variable or wrote generalised responses involving the impact of music listening on driving situations.

(d) Unfortunately, although candidates seemed aware that the driver.s reaction time would be affected by drowsiness, many did not state that the time would increase. There were many answers in terms of distances which received no credit.

(e) Almost all candidates gave the correct answer.

E20. (a) This question was answered well with a majority of the candidates achieving both marks. However, there were some responses which indicated that candidates had interpreted ‘m/s’ as being momentum per second. Some candidates thought that R had the most momentum because it was in front.

(b) (i) Most candidates were able to multiply the mass by the velocity correctly. However, a significant minority of candidates substituted the numbers correctly but seemed not to have a calculator to enable them to give the correct answer.

(ii) The majority of candidates responded correctly with errors being equally split between the two wrong answers provided. A few candidates had unfortunately tried to split the correctly paired unit circling only either kg or m/s.

(c) (i) This question was answered well with most candidates responding in terms of an increase in reaction time although some incorrect responses were clearly directed towards distance, rather than time.

(ii) This question was poorly answered mainly due to candidates not answering the question set ie, what happens to braking distances in wet conditions.

Candidates wrote excellent responses in terms of aquaplaning, skidding, lack of traction, wet brakes, the need to brake earlier, the need for less braking force, the increased possibility of accidents, the need to drive slower, etc. However, these responses failed to address the question.

E21. (a) Many candidates obtained the correct answer having correctly calculated the resultant force as 1155 N. Correct calculation of the force 1155 N then multiplying by the mass of 275 kg was a common error gaining just one mark. The use of an incorrect force with the correct method, gained many candidates one compensatory mark.

(b) (i) Many candidates failed to understand that the question was referring to the validity of the data with many answers given in the form of a conclusion rather than answering the question about valid data. Those candidates who realised the question was about the data, answered mainly in terms of the reliability of police files (YES) or on the lack of information about ages (NO). Many candidates quoted the number of files in the source, but as they failed to express whether this was a large or a small sample, failed to score a mark for this. There was also evidence of much rewriting of answers, mostly to little or no advantage.

(ii) Just over half of candidates gained one mark for describing how the smaller motorbikes had more accidents and a small minority of candidates went on to note

how there were fewer smaller bikes than larger bikes, or calculated ratios.

(c) (i) Very few candidates gained full marks on this question, in spite of it being a well examined aspect of the course. A change in context does disguise what is needed to all but the highest scoring candidates, in spite of the stem referring to momentum. Over half of candidates scored zero. The quality of the explanation was often poor. There are still a large number of answers referring to cushioning the impact rather than reducing the force. The‘decreases rate of change of momentum’ is the most frequently missed mark. A number of candidates confused their response with references to kinetic energy and stopping distances.

(ii) Most candidates gave the answer that the new safety barriers would save lives, or reduce injuries, which gained the mark. Those who thought that 17m/s was too slow to crash or cause serious injury had confused the unit with mph.‘Money could be better spent’ was rarely a complete answer and so did not score a mark very often.

E22. (a) This question was generally answered well with virtually all candidates recognising that drinking alcohol would increase the chance of an accident occurring. However, a number of candidates failed to achieve the second mark due to identifying that there would be an alteration of the driver’s reactions, but not whether the alteration would be positive or negative. Another common error was to state that the ‘driver’s reaction time decreases’.

(b) Virtually all candidates understood the idea that a fair test was required to choose the best barrier to slow a car and not break. However few were able to explain how a change of the three different variables would affect the outcome and prevent a valid set of results being produced, that would provide evidence to which crash barrier was the best of the three under trial.

(c) Just over four fifths of candidates chose the correct answer.

E23. (a) Nearly 60% of students scored all three marks. However, “standing still” or “stationary” was a common wrong answer to A, even though the students were told the car was moving. Often, in B and C, students calculated the resultant force and did not describe the motion, just the direction; forwards for B or backwards for C.

(b) (i) Most students correctly gave the distance travelled while braking. Some students correctly wrote about the distance travelled after braking, or distance travelled in the braking time. A common wrong answer was to involve total distance travelled before the car stops, since this would include the reaction time. Many students lost the mark by putting a list of “braking and stopping distance”.

(ii) Only 25% of students scored this mark. Students often wrote about factors affecting stopping and braking distance; ‘bad weather conditions’ was a very common wrong answer. Also tiredness, being drunk, condition of road and state of vehicle were often given.

(c) (i) This mark was for giving both 5000 N and a clear direction. A lack of a simple arrow drawn in the correct direction kept many students from gaining this mark. Some students simply wrote ‘a very large force’ rather than quantifying it. A common incorrect answer was “5000 N on the car”. One of the most common responses was “5000 N towards the car”, which gained credit. Some students failed to include 5000 N in their answer, just stating that the resultant force was equal and opposite.

(ii) This question is about a dummy being used to measure/record the effects of impact/force. Many students wrote around this answer. “To see the force” was a common incorrect answer. Many students answered in terms of how much damage the dummy received, not mentioning measurement of the forces causing the damage and many students wrote about “impact”, instead of “force”, and did not gain credit for their answer.

(iii) A great number of students knew how to find the gradient of a velocity-time graph in order to calculate the acceleration, However, they failed to use only the straight line part of the graph - between 2 and 4 seconds. As a result, 10/4 was a common answer, giving 2.5 instead of 4. Often, the unit was the only credit-worthy part of an answer, although there were a number of mps, mph, km/s, etc. An answer of 40 was also quite common, multiplying 10 by 4. About half the students gave the correct unit; although m/s was a common incorrect answer. Some students drew a triangle correctly, but failed to use it, gaining one mark only. Some students correctly found 2 and 8, or 1 and 4, but then didn’t know how to calculate the acceleration; obtaining 16 or 0.25.

E24.(a) (i) Two thirds of the students scored the mark for this question. A common mistake was to refer to slower reaction time or to braking distance. Some students failed to describe the increased thinking time adequately writing about it taking, for example ‘longest to brake’.

(ii) This was answered correctly by just over half of the students, the most common correct response being cited as ‘the same slope / gradient’.

(iii) A third of the students gained all 3 marks with only a very low number gaining 2 marks for showing clear working with an incorrect numerical answer. A small number of the students gained one mark, usually for identifying the additional reaction time as being 0.8 seconds. There were many incorrect calculations, often based on using the equation for the area of a triangle to calculate the entire area beneath the graph.

(b) A minority of the students gained both marks; a majority were able to identify Z as the correct sensor but most cited the resistance and the force being directly proportional as the reason.

E25.(a) Nearly all students were able to add the two numbers to give the correct stopping distance.

(b) (i) A significant number of students either misunderstood the graph or thought that ice on the road would decrease the braking distance and so drew a line below that given.

(ii) About three quarters of the students correctly identified ‘Rain on the road’.

(c) (i) The majority of students were able to match the drivers to the correct graph line to gain both marks.

(ii) Few students scored both marks, however over half did score one mark by realising that the information for driver C did not distinguish between the two conditions.

E26.(a) Most students scored at least one mark, for referring to the more streamlined profile of design Y, and many went on to talk about the effect of air resistance. Nearly half of the students then referred their answer back to the effect on the top speed to gain full marks.

(b) (i) The majority of students were able to make the calculation accurately but many lost a mark by failing to give their answer to 2 significant figures. Many students incorrectly rounded down or put 1.6 recurring, denoted by a dot, not appreciating that this was not 2 significant figures.

(ii) This was poorly answered with the majority of the students scoring zero.

(iii) Less than half of the students answered this correctly.

E27.(a) Most students gave a correct answer. The only common incorrect responses seen were gravitational potential and gravitational potential energy.

(b) This was well answered with most students gaining at least two marks. Most students identified that the car was accelerating and that the distance between the oil drops was increasing. Fewer students appreciated that the oil drops falling at regular time intervals was also relevant to confirming that the speed was increasing.

(c) (i) Over half of the students gave a relevant factor. Students failing to gain the mark usually gave thinking time / distance or a factor that affects thinking distance.

(ii) Very few students were able to complete all the steps required in order to gain all three marks. Many students failed to change the 3 kN value to 3000 N, but some of these students went on to give an answer of 75 with the unit kJ and so did score full marks. However it was more common for the answer 75 to have no unit attached or an incorrect one, N/m being common.

E28.(a) (i) Only one quarter of students gained this mark, the majority of students starting their answer with ‘The time it takes for the driver …’

(ii) A majority of students gained both marks, with most mentioning use of a mobile phone causing distractions as one of their answers. A number of students confused thinking and braking distance, giving weather or road conditions as an effect on thinking distance.

(b) (i) This was well answered with the vast majority of students scoring both marks. A common error was failing to square the speed. This was surprising as the students had usually quoted the correct equation.

(ii) Many students completed another operation despite the question being worth only one mark, as a consequence only half of students scored this mark.

(iii) Some students were let down by the inability to rearrange a simple equation or to divide correctly by 8000. However over half of students were able to score both marks.

(iv) The vast majority of students scored this mark. Those who did not usually gave speed, despite the stem of the question asking for one other factor. There were also a number of students who responded with factors affecting the reaction time and thinking distance.

(v) The majority of students scored one mark on this item for either of the two marking points. Unfortunately a number of students did not read the question carefully and gave answers including ‘friction is caused between the road and the car’, scoring zero. There was little appreciation of work being done to stop the car even though this had been introduced in part (b)(ii).

(c) Very few of students scored all three marks. A number of students did not really read the question carefully enough and wrote an answer describing the effects on braking distance and thinking distance. Many students seemed to think the car would go slower so as not to need to brake so much, and related this to increased road safety. There were many confused answers and students should be encouraged to plan answers to focus on one aspect at a time.

E29.(a) Nearly all students scored at least one mark with nearly half of students scoring both. The most common error was writing distance in the second answer space.

(b) Only just over half of the students gave the correct answer. The most common incorrect answer was ‘The car driver being tired’.

(c) (i) The majority of students who scored one mark on this question correctly identified that braking distance increases with speed but added no further detail to allow them to score the second mark.

Those candidates who scored two marks generally gained the second mark for quoting two points of numerical data from the graph. Students scoring zero were generally making comments about thinking distance increasing with speed or stopping distance increasing with speed.

(ii) A wide variety of lines were drawn, however most were acceptable. Most students did seem to know that in icy conditions the braking distance would increase but a large number of students did not follow the shape of the curve given.

(d) (i) This was well answered by the minority of students who realised that reaction time did not change with speed. There were a number of students who confused ‘thinking distance’ with thinking time or reaction time and therefore did not score the mark because this would change with speed.

There were a worrying number of students who thought you would react quicker when driving faster because you would concentrate more.

(ii) This was poorly answered, most students did not realise that the evidence required monitoring of the roads in question and suggested collecting data about other roads.

There were also a number of students who thought that accident levels on any 20 mph road could be compared with other 30 mph roads to use as evidence not appreciating that other differences in conditions would make that data invalid. Almost no students mentioned the requirement of gathering data over the same period of time, before and after the speed limit was introduced. A number of students thought that repeating tests on stopping distances from different speeds was required.

E30.(a) (i) Three-quarters of students knew that the energy possessed by a car at the top of a slope is gravitational potential.

(ii) Nearly all students knew that the energy the car possessed after rolling down the slope was kinetic.

(b) (i) Just over half of the students knew that the acceleration on a velocity-time graph of the car slowing down on a horizontal surface, was represented by its slope. There were many vague statements like ‘the line’.

(ii) Three quarters of students knew that the distance travelled on a velocity-time graph was represented by the area under the graph.

(iii) Students were asked to draw a second line on the velocity-time graph to show the motion of the car if its brakes had been lightly applied when it reached the bottom of the slope. This was very well answered with three-quarters of the students gaining full marks.

(c) (i) Students had to calculate two values of average speed for two trolleys from two sets of values of distance and time.

Three-quarters of the students were able to calculate the average speeds, but only a fifth of them gave the answers to two significant figures. In such situations students, are expected to give the answers to a suitable number of significant figures to match the other data in the table.

(ii) Students had to state and justify whether the distances, velocities and accelerations for the two trolleys were the same.

The distances were not the same because two different values had been given.

The speeds were the same to two significant figures. Because students usually had correct values of 31.0 and 30.8 for the velocities, they often argued that these values were not the same. In future, students will be expected to exercise better judgment in experimental situations and consider whether values are, more than, for example, 5% apart.

Despite the trolleys slowing down from the same initial velocity in different times and distances, many students stated that there was not enough evidence to judge whether the negative accelerations were the same.

Despite that, a third of the students did score full marks.

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Web viewThe force of friction between the brake pads and the steel discs gradually stops the car