2012/PJC/PHYSICS/9646 Turn Over

2012/PJC/PHYSICS/9646[Turn over

Data

speed of light in free space, ms–1

permeability of free space, Hm–1

permittivity of free space, Fm–1

Fm–1

elementary charge, C

the Planck constant, Js

unified atomic mass constant, kg

rest mass of electron, kg

rest mass of proton, kg

molar gas constant, JK–1mol–1

the Avogadro constant, mol–1

the Boltzmann constant, JK–1

gravitational constant, Nm2kg–2

acceleration of free fall, ms–2

Formulae

uniformly accelerated motion,

work done on/by a gas,

hydrostatic pressure,

gravitational potential,

displacement of particle in s.h.m.,

velocity of particle in s.h.m.,

mean kinetic energy of a molecule

of an ideal gas,

resistors in series,

resistors in parallel,

electric potential,

alternating current/voltage,

transmission coefficient, where

radioactive decay,

decay constant,

1(a)State the principle of conservation of momentum.

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...... [1]

(b)Fig. 1.1 showsmomentum against time graphs for two colliding trucks A and B.

Fig. 1.1

The masses of trucks A and B are 2000 kg and 4000 kg respectively.

(i)Explain why the gradients of the graphs during the collision have opposite sign.

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...... [1]

(ii)Show that momentum is conserved when the two trucks collide.

[1]

(iii)Calculate the force acting on truck A during the collision.

force= ...... N [2]

(iv)Using appropriate calculations, determine the type of collision that the trucks experience.

type of collision: ......

...... [3]

(c)Discuss how seat belts and air bags ensure greater safety.

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...... [2]

2(a)Define simple harmonic motion.

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...... [2]

(b)A rubber duck is floating in a swimming pool. When it is pushed down into the water without totally submerging it, and released, it bobs up and down in simple harmonic motion. The variation of the displacement y of the rubber duck with time t is shown in Fig. 2.1.

Fig. 2.1

On Fig. 2.2, sketch a fully labelled graph showing the variation with time t of the kinetic energy of the rubber duck of mass 92.1 g for one period.

Fig. 2.2

[2]

(c)The period T of the oscillating rubber duck, measured in s, is given by

where m is in kg and k = 21 kgs−2.

(i)Surface water waves of speed v and wavelength 0.28 m are incident on the rubber duck. It is noted that the rubber duck is oscillating up and down with maximum amplitude. Determinev.

v = ...... ms−1 [2]

(ii)If an oscillator is used such that more water waves of the same amplitude are incident on rubber duck per unit time, describe and explain what happens to amplitude of the vertical oscillations of the rubber duck.

......

...... [2]

3(a)Describe briefly how the pattern from the two-source interference of light supports the wave theory of light.

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...... [2]

(b)Two microwave sources and are situated as shown in Fig. 3.1.

Fig. 3.1

A detector is placed on a line XY which is parallel to the line joining and . M is the midpoint of the line joining and . The line from M, perpendicular to the line , meets XY at O.

and are switched on together. Fig. 3.2 shows a plot of the intensity of the signal detected along XOY.

Fig. 3.2

(i)What evidence from Fig. 3.2 suggests that the two sources and

are anti-phase to each other,

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...... [1]

do not have exactly the same amplitude?

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...... [1]

(ii)Calculate the length XY given that is 20.0 cm, the distance MO is 10.0 mand the wavelength used is 2.0 mm.

length XY= ...... m [2]

4(a)With reference to a point in an electric field, define the term electric potential.

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...... [1]

(b)Two identical negatively charged particles X and Y, each of mass kg and charge C are held at a distance m apart.

(i)Calculate the electric potential energy of the system.

electric potential energy= ...... J [2]

(ii)If the charges are released, they will move apart. Show that their speed when they are very far apart isms−1.

[3]

(iii)With the two charges held at rest at m apart, a third charge Z is placed at the mid-point along XY so that the system of charges is stationary.

1.State and explain the sign of the third charge in order for the system of charges to be stationary.

......

...... [2]

2.Calculate the magnitude of charge Z.

magnitude of charge Z = ...... C [2]

5(a) By drawing an energy band diagram, describe how p-type doping affects the number of mobile charge carriers of an intrinsic semiconductor.

......

...... [3]

(b)A junction is formed between slices of p-type and of n-type semiconductor material, as shown in Fig. 5.1.

Fig. 5.1

On Fig. 5.1, draw

(i)an arrow to show the direction of movement of electrons as the two slices are brought into contact, [1]

(ii)the symbol for a battery, connected so as to decrease the width of the depletion region. [1]

(c)Fig. 5.2 shows an ohmic resistor connected in series with a semiconductor diode.

Fig. 5.2

The input signal varies with time as shown in Fig. 5.3.

Fig. 5.3

(i)On Fig. 5.4, sketch the variation of the output signal with time tacross the resistor.

Fig. 5.4

[1]

(ii) On Fig. 5.5, sketch the variation of with timetfor the output signal.

Fig. 5.5

[1]

(iii)Calculate the average value ofacross the resistor.

average value of = ...... V2 [2]

(iv)Hence, calculate ,the r.m.s. value of the potential difference across the resistor.

= ...... V [1]

6A homopolar generator comprises an electrically conductive disc that rotates in a plane perpendicular to a uniform static magnetic field.

In order to rotate the disc, a d.c. power supply is connected to the disc, as shown in Fig. 6.1. The disc is placed horizontally in a downward magnetic field and current passes from the axle to the rim of the conducting disc. Fig. 6.2 shows the top view of the disc.

Fig. 6.1Fig. 6.2

(a)(i)State the direction of rotation of the disc in Fig. 6.2.

...... [1]

(ii)As the disc speeds up, there is an increasing e.m.f. induced between the axle and the rim of the conducting disc. Explain why there is an increasing induced e.m.f.

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...... [2]

(b)When the power supply is disconnected, this induced e.m.f. can be used to drive a current through an external resistor, as shown in Fig. 6.3.

Fig. 6.3

State whether the output of a homopolar generator is an alternating current or direct current.

...... [1]

(c)A large homopolar generator can be designed to produce a large current surge when it is short-circuited. Fig. 6.4 shows a current surge from a short-circuited homopolar generator.

Fig. 6.4

(i)Explain the meaning of the term “short-circuited”, as used in the passage.

......

...... [1]

(ii)Estimate the charge that flows during this surge.

charge = ...... C [3]

(iii)Calculate the maximum power dissipated in the generator when the terminals of the generator, which has an internal resistance of 0.12 mΩ, are connected together through a negligible external resistance.

maximum power = ...... W [2]

(d)The magnitude of the induced e.m.f.E can be calculated from the relationship

whereand are the radii of the disc and axle respectively, and B is the magnetic flux density, assumed to be uniform over the surface of the disc.

(i)Determine the units for k.

units for k= ...... [3]

(ii) Hence, suggest what physical quantity may be represented by the symbol k.

...... [1]

(e) State the energy transformation that takes place in the process shown

(i)in Fig. 6.1,

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...... [1]

(ii) in Fig. 6.3.

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...... [1]

7The bouncing of a ball is a requirement for some ball games. With all other variables kept constant, the relation between the first rebound height h of a ball off a surface and the air pressure p inside the ball is

where k and n are constants.

You are provided with a bicycle pump. You may also use any of the other equipment usually found in a Physics laboratory.

Design an experiment using different pressures to determine the value of n.

You should draw a labelled diagram to show the arrangement of your apparatus. In your account you should pay particular attention to

(a)the equipment you would use,

(b)the procedure to be followed,

(c)the control of variables,

(d)how the first rebound height would be measured,

(e)any precautions that would be taken to improve the accuracy of the experiment.

[12]

Diagram

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2012/PJC/PHYSICS/9646[Turn over