AQA - GCSE Physics Revision

Additional Physics (P2)

Chapter 1 - MotionWhat you need to know:• Distance-time Graphs

• Finding out when an object is stationary• Finding out when an object is moving at a constant speed

• Velocity and Acceleration• The difference between speed and velocity• What acceleration is and its units• What is deceleration

• Velocity-time Graphs• Finding out if an object is accelerating or decelerating • What the area under a velocity-time graph represents

• Using Graphs• Calculating speed from a distance-time graph• How we can calculate distance from a velocity-time graph• Calculating acceleration from velocity-time graphs

Distance-Time Graphs

Speed on a distance time graph is represented by the slope

A Constant Speed: An object moving at the same speed travels the same distance every second

Speed 1 = fast moving object (steep line)Speed 2 = steady moving object (straight sloped line)Speed 3 = stationary object (horizontal line)

Velocity and AccelerationVelocity: speed in a given direction (2 objects can have the same speed but a different velocity due to the direction they are travelling in)

Acceleration: the rate at which the velocity of an object is increasing

• An object travelling at a steady speed is accelerating if its velocity is changing• Deceleration = the velocity decreases (negative acceleration) and the object

slows down

Velocity-Time GraphsDistance Travelled = area under velocity-time graph

Acceleration and Deceleration = gradient of the lines

Finding the area under the graph1. Break the area under the graph up into sections and

work out the area of separate shapes2. Once you have worked out the area of each shape

add them together

*If you are only finding out the acceleration or deceleration you only need to work out the gradient of the sloping line (so only

one triangle) Deceleration = -distance / time*

Deceleration on a distance time graph

SummaryHow fast = VelocityHow far = Distance

How quickly the velocity changes = acceleration

Object moving at a constant speed = an increased distance

Chapter 2 – Speeding up and Slowing Down

What you need to know:• Forces Between Objects

• When two forces interact what can we say about the acting forces• What is the unit of force

• Resultant Forces• What is the resultant force• What happens when the resultant force is zero and what happens when it is

not zero• Force and Acceleration

• How acceleration depends on the size of the resultant force• What effect the mass of an object has on acceleration

• On the Road• The resultant force of a vehicle travelling at a constant velocity• What the stopping distance of a vehicle depends on and how the stopping

distance can be increased• Falling Objects

• What is the difference between mass and weight• What is the terminal velocity

Forces Between ObjectsForces can:

Twist Pull

Push

Upthrust

Weight/Gravity

Thrust Friction

Forces are measured in Newtons (N) They act in pairsEach force acts in a certain directionWhen two forces interact with each other they always exert equal and opposite forces on each other

Resultant ForceResultant Force: working out the effect each force has on an object. This force has the

same effect as all the forces acting on the object

Object at the Start Resultant Force Effect on the

Object

1 (glider) At rest Zero Stays at rest

2 (moving a crate)

Moving Zero Velocity stays the same

3 (plane) MovingNon-zero in the same

direction as the direction of the moving object

Accelerates

4 (car breaking) Moving

Non-zero in the opposite direction to the direction

of the moving objectDecelerates

Force and Acceleration

Resultant Force (N) = Mass (kg) x Acceleration (m/s²)

FAM

Mass Acceleration

Force

The velocity increases if:• The resultant force is in the same direction as the velocity• The velocity is positive

The velocity decreases if:• The resultant force is in the opposite direction as the velocity• The velocity is negative

Acceleration depends on:The mass of an object

The amount of force applied

On the RoadThinking Distance: distance travelled by the vehicle in the time taken for the driver to

reactBraking Distance: distance the vehicle travels under the breaking force

The breaking force needed to stop a moving vehicle depends on:• The velocity of the vehicle• The mass of the vehicle

Stopping Distance = Thinking Distance + Braking Distance

Factors affecting the stopping distance are:

• Tiredness• Alcohol and Drugs

• Adverse Road Conditions• A Poorly Maintained Vehicle

Affect Thinking Distance

Affect Breaking Distance

Falling ObjectsWeight: the force of gravity upon an object (N)

Mass: the quantity of matter in it (kg)

Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg))

The weight of an object:• Of mass 1kg = 10 N• Of mass 5kg = 50 N

The Earths gravitational field strength is 10 N/kg

If an object falls freely:• No other forces act upon it, therefore the resultant force is its weight. A 1kg

object would accelerate at a constant acceleration of 10m/s² (force ÷mass) on previous slide

If an object falls in fluid:• The fluid drags on the object, and the drag force increases with speed• The resistance is weight – drag force• When the drag force and velocity are equal the object reaches a terminal

velocity (the resultant force is 0 so the acceleration is 0)

Chapter 3 – Work, Energy and MomentumWhat you need to know:• Energy and Work

• What do we mean by ‘work’ in science• What is the relationship between work and energy• What happens to the work done against frictional forces

• Kinetic Energy• What is kinetic and elastic potential energy• How does the kinetic energy of an object depend on its speed• How can we calculate kinetic energy

• Momentum• How can we calculate momentum and what is its unit• What happens to the total momentum when two objects collide

• More on Collisions and Explosions• Why does momentum have a direction and size• When two objects fly apart why is their total momentum 0

• Changing Momentum• What does a force do to the momentum of an object• How can we calculate the change in momentum caused by force

Energy and WorkWorkdone: when an object is moved by force we say that work is done to the object

It can also be the energy transferred/change in gravitational potential energy

Work Done/Energy Transferred (J) = Force (N) x Distance (M)

WDF

ForceDistance

Work Done

Change of Gravitational Potential Energy(J) = Weight (N) x Change in Height (M)

GHW

Weight Height

Gravitational Potential Energy

Kinetic EnergyElastic Potential Energy: the energy stored in a elastic

object when work is done on the object

Kinetic Energy (J) = ½ [Mass (Kg) x Speed²(m/s)] KE = ½ mv²

An object is elastic if it regains its shape after being stretched or squashedExamples of this are:• Bow and arrow• Elastic band• Spring• Rubber swimming hats

MomentumMomentum: the ability for an object to keep moving (relating its mass and velocity) in

the same direction

Mass in motion

The momentum of a moving object(Kg m/s) = Mass (Kg) x Velocity (m/s)

PVM

MassVelocity

MomentumIt is difficult to change the direction of movement of an object with a lot of momentum Momentum is conserved whenever objects interact, as long as no external forces act on them

What happens when two cars of the same mass collide?• If cars have a combined mass of

1000kg• Momentum is conserved (stays

the same)• Velocity of car 1 is halved by

impact

More on Collisions and ExplosionsMomentum has a size and a direction

When two objects push each other apart, they move apart with equal and opposite momentum

(Momentum of A) = -(Momentum of B) (Mass of A x Velocity of A) = -(Mass of B x Velocity of B)OR

As it is travelling in the opposite direction

Changing MomentummThe more time an impact takes, the less force is exerted

Chapter 4 – Static ElectricityWhat you need to know:• Electrical Charges

• What happens when insulators are rubber together• What is transferred when objects are charged• What happens when charges are brought together

• Charge on the Move• Why metals cant be charged by rubbing them• How charge is transferred through conducting materials• What happens when a charged conductor is connected to earth• Why do some objects sometimes produce sparks

• Uses and Dangers of Static Electricity• In what ways is static electricity useful• How can static electricity be dangerous• How can we get rid of dangerous static electricity

Electrical ChargesVan de Graaff GeneratorThe dome charges up when the generator is switched on. Sparks are produced if the charge becomes to great. Charge builds up in the dome because:• The belt rubs against the

felt pad (FRICTION)• The belt carries the

charge onto the insulated metal dome

• Sparks are produced when the dome can not hold any more charge

Charging by FrictionRubbing two insulators together causes them to become chargedFriction causes electrons to be transferred from one material to the otherIf a material:• Gains electrons it becomes

negatively charged• Looses electrons it becomes

positively chargedA Polythene Rod transfers electrons from the cloth to the rodA Perspex Rod transfers electrons from the rod to the cloth

In the exam they will say which insulator carry’s which charge, unless it specifies which type of rod is being used (here you need to know which insulator transfers electrons)

Charge on the MoveElectrical Current: the rate of the flow of charge

Conductors can only be charged if they:• Off of the ground

Insulators can only be charged if they:• Brought into contact with a charged object

If it is not insulated from the ground, it wont hold charge as electrons transfer between the

conductor and the ground

Discharging an ObjectTo discharge an object you have to provide a path between the conductor and the groundThe path between the object and the ground allows the electrons to flow to the ground – this object is then Earthed(Shown in the diagram below)

Sparks and StrikesIf a metal object (conductor) gains to much charge it will produce a spark between the conductor and the charged objectThis is because the voltage between the conductor and the ground increaseLighting is an example of this

Uses and Dangers of Static ElectricityUses of Static Electricity Dangers of Static Electricity

Paint Sprayer:The paint droplets are given positive chargeThe car is given a negative chargeThe droplet and car attract each otherThe paint droplets repel each other

Transporting Oil:If the pipe is not earthed, a build up of charge could cause a sparkIf there is a spark, an explosion could occur

Photocopier:Drum is positively charged until light falls on itCharge is lost in the area where light hits itBlack toner sticks to the drum where there is still chargePaper is heated to stick the toner to it

Antistatic Floors (in hospitals):Some anaesthetics used in operating theatres are explosive A spark could cause a explosion if any gas has escapedAntistatic material is used on the floor to act as insulator (conducting charge to earth)

Electrostatic Precipitator:

Chapter 5 – Current ElectricityWhat you need to know:• Electric Circuits

• What are the circuit symbols for common components• Resistance

• The placement of ammeters and voltmeters• Resistance and its unit• ‘Ohm’s’ Law• Reversing the current in a resistor

• Current-Potential Difference Graphs• When the temperature changes what happens to the resistance in a filament

lamp and thermistor• How does the current in a diode depend on the potential difference across it• When the light level increases what happens to the resistance of a LDR

• Series and Parallel Circuits• The current and potential difference of components in a series circuit and

parallel circuit• Why cells are connected in series• Finding the total resistance of a series circuit and parallel circuit

Electric Circuits-Symbols

A component diagram shows how the components in a circuit are connected together

Every component has its own symbol. The ones on this slide and the next are the ones you need for GCSE

ResistanceAmmeter: connected in series with the lamp to measure the current going through the lamp

Voltmeter: connected in parallel to measure the potential difference across the lamp

The current through a resistor of a constant temperature is directly

proportional to the potential difference across the resistor

Resistance (ohms) = Potential difference (volts) Current (amperes)

Current-Potential Difference GraphsThermistor: does no obey Ohm’s Law (is not a straight line) and a reverse of the filament lamp. More current = steeper graph, more heat = more free electrons to carry the current = increased current = reduced resistance

Filament Lamp: does not obey Ohm’s Law (it is not a straight line) more current = hotter = atoms vibrate faster increasing collisions with electrons = increased resistance (shown by the flattening out of the graph)

LDR: semi conductor. Increase in light = more electrons carrying current = increasing current = reduced resistance, little light = less electrons carrying current = reducing current = increased resistance

Diode: does not obey Ohm’s Law (is not a straight line) connected in a forward direction = low resistance, connected in the reverse direction = high resistance

Series Circuit

The current is the same through all components in series with each otherThe total potential difference/ the voltage supply in a series circuit is shared between

the componentsThe total potential difference/ the voltage supply of the cells is the sum of the

potential difference/ the voltage of each cellThe total resistance and the components in series is the sum of their separate

resistances

Parallel Circuit

1. The total current through the whole circuit is the sum of the currents through the separate components

2. For components in parallel, the potential difference/ the voltage across each component is the same

3. The bigger the resistance of a component the smaller the current

Chapter 6 – Mains ElectricityWhat you need to know:• Alternating Current

• What direct and alternating current is• Frequency of the UK mains supply• Using an oscilloscope

• Cables and Plugs• The casing of a mains plug• The colour of the different wires in a plug• Which wire is connected to different pins in a plug

• Fuses• What are fuses and circuit breakers used for• Why do we have to use a fuse with the correct rating• Why appliances in plastic cases don’t need to be earthed

• Electrical Power and Potential Difference• How to calculate the power of an appliance using energy and time• How we can calculate electrical power and its units• Finding the total resistance of a series circuit and parallel circuit

• Electrical Energy and Charge (Higher)• What is electrical current and its charge• What energy transformations take place when charge flows through a resistor

Alternating Current (a.c)Alternating Current: a current which repeatedly reverses in direction

You can measure the alternating potential difference using an oscilloscopeYou can also see the peak potential difference as well as the frequency of an alternating current (Higher)

In the UK the frequency of mains electricity is 50 cycles per second (50hz)Mains electricity uses an alternating currentIn a mains circuit there is a live wire which is alternately positive and negative every cycle and a neutral wire which is always at 0 volts

Frequency = 1

Time (sec)

Cables and PlugsLive Wire – is brown and connected to the live pin

Neutral– is blue and connected to the neutral pin

Earth Wire – is yellow and green and connected to the earth pin (a two core cable does not have a earth wire) which is the longest pin in the plug

The pins in a plug are made of brass

The cable is copper but is surrounded by an insulator such as rubber/flexible plastic

The case of the plug is made out of stiff plastic

Earth wires are essential for appliances with metal cases. If the live wire becomes loose and touches the metal case a large current flows to earth, blowing the fuse and breaking

the circuit

FusesA fuse is a safety device which breaks the circuit if the current becomes to highIt contains a thin wire which melts (breaking the circuit)

The fuse sits next to the live wire

It is important that you use the correct amp fuse in your appliance.If a larger fuse in used, the fuse will not blow when it is supposed to and the heating effect on the appliance could result in the appliance catching alight

Circuit BreakersA circuit breaker is an electromagnetic switch that cuts the current off is the current is too great After being used it can be resetCircuit breakers work faster the fuses and are sometimes fitted into ‘fuse boxes’ to replace fuses

Electrical Power and Potential DifferencePower: energy transferred per second

The power (watts) is the energy transformed (joules) every second, using the equation below:

Power (W) = Energy (J)

Time (S)E

TP

To make a light bulb shine brighter you can:• Increase the voltage (increase the energy delivered)

• Increase the current (increase the rate at which energy is delivered)

We can also calculate power dissipated (lost) in a device, using the equation below:

Power (W) = Current (A) x Voltage (V) PVI

Current

Electrical Energy and ChargeElectrical Current: the rate of flow of charge (measured in Coulomb [C])

The charge of an appliance can be calculated using the equation below:

Charge Flow (C) = Current (A) x Time (S)C

TICurrent

Resistor is connected to

battery

Electrons pass through the

resistor from the battery

Electrons are ‘resisted’ by the

resistor

The atoms in the resistor gain

kinetic energy

The resistor gets hot (electrical

energy transferred as heat)

We can calculate the energy transformed using the equation below:

Energy Transformed (J) = Potential Difference (V) x Charge Flow (C)E

CV

Chapter 7 – Nuclear PhysicsWhat you need to know:• Nuclear reactions

• How does the nucleus of an atom change when it emits and alpha or beta particle

• How can we represent a nuclear reaction• Where does background radiation come from

• The Discovery of the Nucleus (Higher)• How was the Nucleus model of the atom established• What other models of the atom were there

• Nuclear Fission• What radioactive isotopes are used in nuclear power stations• What is nuclear fission• How is nuclear hear produced in a power station• What are fission neutrons

• Nuclear Fusion• Where does the Sun’s energy come from• What happens during nuclear fusion• Why is it difficult to make a nuclear fusion reaction

Nuclear ReactionsAlpha particles have 2 protons and 2 neutrons

An unstable particle becomes more stable by emitting an α particle

4

2α

0

-1β

Neutron changes into a proton (neutron lost = proton gained)Electrons is created and emitted

Gamma radiation (which has no mass) is also given off by unstable nuclei after alpha and beta radiation is given off

Background radiation:• Nuclear weapons testing• Nuclear power stations• Radioactive rocks – some

of which give of radio active gases

The Discovery of the NucleusJohn Dalton reintroduced the idea that everything was made of atoms• He said atoms were solid spheres of matter that could not be split

Thomson adapted Dalton’s model• He said that an atom is a positively charged sphere with negative

electrons distributed through it (plum pudding model)

1914 the nucleus was discovered

Alpha particles in a beam are sometimes scattered through large angles when they are directed at a thin metal foil e.g. gold foil

Rutherford’s gold foil experiment, meant the following could be discovered using his results:• The nucleus was positively charged as it repels

the α particles (like charges repel like magnets)• Much smaller than the atom because most α

particles pass through it without deflection• Where most of the mass of the atom is located

The paths the α particles take

Nuclear FissionNuclear Fission: the splitting of an atomic

nucleus

There are two elements, which cause nuclear fission when their nucleus split:

Uranium 235Plutonium 239

When one fission actions occurs, the process repeats until the nucleus becomes stable, a chain reaction takes placeNuclear fission is an un-natural processIn a nuclear reactor one neutron per fission (on average) goes on to produce further fission

Both used in making nuclear weapons

Nuclear Reactor

Nuclear FusionNuclear Fusion: when two nuclei are forced close enough together so they form a single

larger nucleus

Energy is required to make nuclear fusion occurEnergy is also released when two nuclei are fused together (which could be used to produce electricity)Fusion reactors need to be at very high temperatures before nuclear fusion can take place Fusion takes place in the sun, as the core is so hot it consists of nuclei without electrons resulting in them fusing together when they collide with enough kinetic energy otherwise they will repel each other

Inside Fusion ReactorsThe gas is heated by passing an electric current through it The gas becomes so hot is forms a plasma of nuclei The plasma is contained using a magnetic field to prevent it from touching the container wallsWhen hydrogen nuclei are fused together, helium is formed Fusion reactors are safer than fission reactors as:• The products (helium)

are not radioactive therefore are stable

• If the plasma touches the sides it immediately cools, meaning fusion can no longer take place