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SIR MICHELANGELO REFALO

SIXTH FORM

Half-Yearly Exam 2016

Subject: Physics ADV 1ST

Time: 3hrs

Take the acceleration due to gravity g = 9.81ms-2

Section A

Attempt all questions in this section

1. a) Classify the following as base or derived SI units:

The newton, the joule, the ampere, the volt , the watt and the second. 3 marks

b) Schwarzschild used Einstein’s general theory of relativity to derive an expression

for the critical radius RS of a black hole. The Schwarzschild radius is

RS =

Where RS is measured in metres, G is called the gravitational constant having units

Nm2kg

-2, M is the mass in kg and c is the speed of light. Check that the equation is

homogeneous with respect to its base units.

4 marks

2. A friend of yours who is not a student of physics refuses to accept that forces must

always occur in pairs. He gives some examples to disprove this idea:

a) A stone falling from a cliff. 2 marks

b) A nail being driven into a piece of wood by a hammer. 2 marks

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c) A car accelerating from rest on a road 2 marks

Your friend says it is obvious that in each of these cases there is only one object that

clearly has a force exerted on it, and that is the only force there is.

Use your understanding of Newtonian physics to explain why he is wrong in each

case. Draw free body force diagrams to explain your answer. Moreover, state

another three principal characteristics of a Newton’s third law pair of forces.

3 marks

3. a) Explain the term average drift velocity as used in the context of metallic

conduction. 2 marks

b) Derive an expression for the current in a metal conductor in terms of the average

velocity v, the electronic charge e, the cross sectional area A of the conductor and its

density of charge carriers n. 5 marks

c) A silver wire 1.0mm in diameter transfers a charge of 72.0C in

1hour,15.0minutes. Silver contains 5.80 x 1028

free electrons per cubic metre.

i) What is the current in the wire? 1 mark

ii) What is the size of the drift velocity of the electrons in the wire? 2 marks

4. a)A galvanometer with an internal resistance of 15Ω and f.s.d. at 20mA is converted

into an ammeter that is capable of reading a current of 10A. Determine the,

a) value of the shunt resistor and 4 marks

b) the total resistance of ammeter 2 marks

c) If the shunt resistor used consists of a wire of resistivity equal to 1.72 x 10-8

Ωm,

and has a diameter of 4 x 10-4

m, find its length. 3 marks

d) Explain how one can convert the galvanometer to a voltmeter that gives f.s.d. of

100V. 2 marks

5. a) What are the conditions for static equilibrium? 4 marks

b) A uniform ladder of mass 40kg and length 10m is leaned against a smooth vertical

wall. A person of mass 80kg stands on the ladder a distance 7m from the bottom, as

measured along the ladder. The foot of the ladder is 1.2m from the bottom of the

wall.

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i) Draw all the forces acting on the ladder. 5 marks

ii) What is the force exerted by the wall on the ladder? 3 marks

iii)What is the resultant force exerted by the floor on the ladder? 3 marks

6. a) State Kirchhoff’s laws. 4 marks

b)The two cells have an emf of 1.5V each. Find the current flowing through both

cells.

5 marks

2.0Ω

1.0Ω

5.0Ω

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7.

a) What can you say about the motion of this object? Describe each section of the

graph. 6 marks

b) Plot the corresponding graphs of acceleration as a function of time and

displacement as a function of time. 6 marks

8. Two identical table tennis balls A and B each of mass 1.5g are attached to a non-

conducting threads of length 0.1m. The balls are charged to the same positive value.

When the threads are fastened to a point P the balls hang as shown in the diagram

and makes an angle of 200to the vertical.

P

A B

a) Draw a labelled free-body force diagram for A. 3 marks

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b) Calculate the tension in one of the threads. 2 marks

c) Show that the electrostatic force between the two balls is 5.36 x 10 -3

N. 3 marks

d) Calculate the charge on each ball. 2 marks

9. a) Explain the principle of operation of a p-n junction diode. 4 marks

b) Sketch I-V characteristic of such a device, identifying the regions of reverse and

forward bias. 2 marks

c) Distinguish between full-wave and half-wave rectification. 2 marks

d) Sketch circuit diagrams for these functions, explaining how they work. 4 marks

e) Draw energy diagrams for an intrinsic semiconductor at room temperature and an

insulator. 2 marks

f) What is meant by n type and p type semiconducting materials? Explain by giving

examples.

3 marks

10. A force extension graph for a brass wire of length 3.44m and cross-sectional area

1.3 x 10-7

m2 is shown below.

a) For what range of extension is Hooke’s law obeyed by the wire? 2 marks

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The diagram shows an arrangement for investigating this relationship between force

and extension for the brass wire

Draw a rough sketch of the diagram and add a suitable apparatus for measuring the

extension of the wire as further masses are added to the slotted hanger.

Show also on the diagram the length that would be measured in order to calculate the

strain in the wire once the extension has been found.

2 marks

b) Calculate the Young modulus for brass 3 marks

c) How much energy is stored in the wire when it has extended by 7.0mm?

2 marks

d) State one energy transformation that occurs as the wire extends 1 mark

e) Use the graph to calculate the tensile strength of brass 3 marks

f) ) Distinguish between ductile and brittle materials. Is brass ductile or brittle?

Explain. 4 marks

Section B

Attempt any two questions

11. a) Select a method for measuring g, the acceleration due to gravity at the

surface of the Earth. For your chosen method:

sketch the apparatus you would use,

state the measurements that you would need to make,

explain how you would make your measurements,

show how you would use your measurements to determine the acceleration.

8 marks

b) State Newton’s 2nd

law of motion. Apply the law to car airbags. 2 marks

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The human body can survive a negative acceleration trauma incident (sudden stop)

if the magnitude of the acceleration is less than 250m/s2. If you are in a car

accident at an initial speed of 96km/hr and are stopped by an airbag that inflates

from the dashboard, over what distance must the airbag stop you for you to survive

the crash?

3 marks

c) The graph in figure shows the velocity of a skydiver as she jumps from a plane.

Describe briefly all regions of the graph from t = 0s till he reaches the ground.

4 marks

d) A body of mass M rests on a rough surface and is pulled by a force T as shown

below.

Body of mass M

Rough surface

The force T is varied and measurements are taken in order to establish the

corresponding acceleration, a, of M. A graph of a against T is plotted as shown

below.

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a) If the frictional force on the body is f and is constant, show that 3mark

a =

T -

b) Hence, use your graph to determine a value for M. 3marks

c) Determine the size of the frictional force f. 2marks

12. a) What do you understand by the terminal p.d. and e.m.f. of a cell. 4 marks

b) A battery of e.m.f. 24 V and internal resistance r is connected in the circuit shown:

24V

A current of 0.5A flows through the 3 ohms resistor. Find:

i. the current flowing through the 6 ohms resistor;

ii. the current flowing through the 12 ohms resistor;

iii. the internal resistance;

iv. the power dissipated by the battery;

v. the reading on the voltmeter. 8 marks

c) Describe an experiment to find the internal resistance and emf of a cell.

Your answer should include:

r

12

3Ω

Ω

6Ω

V

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the circuit diagram,

the procedure,

the equation used,

the graph plotted and

how the value of internal resistance is determined. 8 marks

d)

Find the value of S in order to balance the above bridge circuit. 5 marks

13. a) The Thrust SSC car raised the world land speed record in 1997. The mass of the

car was 1.0 × 104 kg. A 12-second run by the car may be considered in two stages of

constant acceleration. Stage one was from 0 to 4.0 s and stage two from 4.0 s to

12.0s.

i. In stage one, the car accelerates from rest to 44 m/s in 4.0s. Calculate the

acceleration produced and the resultant force required to accelerate the car.

2 marks

15Ω

24

72

10

G

S

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ii. In stage two, the car continued to accelerate so that it reached 280 m/s in a further

8.0 s. Calculate the acceleration of the car during stage two.

3 marks

iii. Calculate the distance travelled by the car from rest to reach a speed of 280 m/s

2 marks

b) In the javelin event, an athlete manages to throw the javelin with an initial speed

of 108 km/hr . The angle to the horizontal at which it is thrown is 420.

i.The javelin is an example of a projectile. What do you understand by a projectile?

2 marks

ii. Convert 108 km/hr into m/s. 1 mark

iii. If the javelin takes 4.2 s to hit ground, determine the height h (above ground) at

which the javelin leaves the athlete’s hand. 3 marks

iv. Work out a value for the horizontal range of the javelin after it strikes the ground.

2 marks

c) State the principle of moments. 2 marks

A shop sign of mass 2·0 kg is supported by a hinged uniform rod and thin

cable as shown.

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The mass of the thin cable is negligible but the rod has a mass of 1·0 kg.

(i) Calculate the total clockwise moment about the hinge. 3 marks

(ii) Hence calculate the tension in the thin cable. 3 marks

(iii) Calculate the horizontal force the wall exerts on the hinge. 2 marks

14. a) Define Coulomb’s law. 2 marks

A tiny negatively charged oil drop is held stationary in the electric field between two

horizontal parallel plates, as shown below. The upper plate has a potential of 200V

and the distance between the plates is 20cm. Its mass is 4x10 -15

kg. The field

between the plates is a uniform field.

i. What do you understand by the statement a uniform field? 2 marks

ii What are the two forces acting on the drop and in which direction do they act?

2 marks

iii Use the fact that the two forces balance to calculate the charge on the oil drop.

3 marks

b) Sketch the electric field pattern

i. between two oppositely charged metal plates 1 mark

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ii. around a positive point charge. 1 mark

What features of your sketch show that the former is uniform while the other

decreases with distance from the point charge? 2 marks

iii. What is the kinetic energy gained by an electron as it is accelerated from

rest through a p.d. of 20kV? Give your answer in eV and Joules. Hence

determine the final speed attained by this electron. 5 marks

c) Define electric field strength at a point in space. 2 marks

Two point charges, +1.6 x 10-19

C and -6.4 x 10-19

C, are held at a distance

8.0 x 10-10

m apart at points X and Y as shown in the diagram.

X Y

8.0 x 10-10

m

P

i. Find the resultant magnitude of the electrical field at point P.

ii. Show the direction of the electrical field at point P. 5 marks

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