Cambridge IGCSE Physics - 0625 - Supplement Paper 4 2017 Summer Zone 3

(a) Acceleration is a vector quantity. Underline the two vector quantities in the list below.
energy force frequency impulse mass refractive index [1]
(b) A car accelerates uniformly from rest at $2.2 \text{ m/s}^2$ for $3.0 \text{ s}$.
(i) Calculate the speed of the car at time $t = 3.0 \text{ s}$.
speed = .............................................................[2]
(ii) At time $t = 3.0 \text{ s}$, it has travelled a distance of $9.9 \text{ m}$.
Calculate the average speed of the car during the first $3.0 \text{ s}$ of the journey.
speed = .............................................................[1]
(iii) On Fig. 1.1, sketch a distance-time graph for the first $3.0 \text{ s}$ of the journey.
[3]

(a) State the word equation that defines \textit{momentum}.
......................................................................................................................[1]

(b) A metal block A, travelling in a straight line at 4.0 m/s on a smooth surface, collides with a second metal block B which is at rest. Fig. 2.1 shows the two metal blocks A and B before and after the collision.



The mass of A is 3.2 kg. The mass of B is 1.6 kg. After the collision, the velocity of A is 1.5 m/s.
Calculate

(i) the momentum of A before the collision,
momentum = ............................................................[2]

(ii) the velocity $v$ of B after the collision.
$v$ = ...........................................................[3]

(c) In the collision that occurred in (b), block A and block B are in contact for 0.050 s.
Calculate the average force that is exerted on B during the collision.
average force = ............................................................[2]

(d) After the collision in (b), the total kinetic energy of the two blocks is less than the kinetic energy of block A before the collision.
Suggest \textit{one} reason for this.
......................................................................................................................[1]

A block of wood has a volume of 210 cm$^3$ and a mass of 180 g.

(a) Calculate the density of the block of wood.

density = .......................................................... [2]

(b) The block is held just above the surface of a liquid of density 0.88 g/cm$^3$.

Predict and explain what happens when the block is released.

.........................................................................................
......................................................................................... [2]

In the braking system of a car, the brake pedal rotates about a pivot when the pedal is pressed. Fig. 4.1 shows part of the braking system.



The driver exerts a force of 200 N on the pedal at a distance 22 cm from the pivot. As the pedal rotates about the pivot, a force is exerted on the piston and the pressure of the oil increases.

The area of the piston in the cylinder is $5.0 \times 10^{-4} \text{ m}^2 (0.00050 \text{ m}^2)$.

Calculate the increase in the pressure of the oil.

increase in pressure = \text{........................................................}[4]

A footballer and a referee are discussing a puddle of water that has formed on the pitch. The footballer wears a white shirt whilst the referee wears a black shirt which, apart from its colour, is identical.

Fig. 5.1 shows the two men looking at the puddle.



The weather is bright and sunny.

(a) State and explain how the temperature of the white shirt differs from the temperature of the black shirt.
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............................................................................................................................................. [2]

(b) The volume of water in the puddle is slowly decreasing.

(i) Describe how two changes in the weather conditions could affect the rate at which the puddle dries.
change 1 ............................................................................................................................
effect .................................................................................................................................
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change 2 ............................................................................................................................
effect .................................................................................................................................
............................................................................................................................................. [2]

(ii) Explain, in terms of the water molecules, what happens as the puddle dries.
.............................................................................................................................................
.............................................................................................................................................
............................................................................................................................................. [2]

Fig. 6.1 shows a child releasing a balloon filled with helium.



The pressure of the helium in the balloon keeps the balloon inflated.

(a) Explain how the particles of helium produce this pressure.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................[3]

(b) As the balloon travels upwards through the atmosphere, the volume of the helium increases. The temperature of the helium remains constant.

(i) State an equation that relates the volume of the helium to its pressure.
.................................................................................................................................[1]

(ii) Fig. 6.2 shows how the air pressure in the atmosphere changes with the height above ground level.



1. Using Fig. 6.2, determine the pressure at ground level. Give the unit.
pressure = ............................................ unit = ........................[2]

2. Using Fig. 6.2, determine the height at which the volume of the helium in the balloon is twice the volume at ground level.
height = ...........................................................[2]

A loudspeaker is built into the side of a swimming pool. The loudspeaker produces sound waves in the water of wavelength 0.25 m.
(a) (i) The frequency of the sound waves is 6.0 kHz. Calculate the speed of the sound waves in water.

speed of sound waves in water = .............................................................[2]

(ii) State a typical value for the speed of sound in air.

speed of sound in air = .............................................................[1]

(iii) State and explain, for the sound produced by the loudspeaker, how the wavelength of the sound in air compares with the wavelength of the sound in water.

[1]

(b) Sound is a longitudinal wave.

Explain what is meant by a longitudinal wave.

[2]

(c) The sound emerges from the loudspeaker through a gap. The sound diffracts as it passes through the gap.
(i) State how the width of the gap affects the diffraction.

[1]

(ii) State how the wavelength of the sound affects the diffraction.

[1]

Red light travelling in air strikes the curved surface of a semi-circular glass block at P. Fig. 8.1 shows the ray of light.

The light travels in a straight line from O to Q.
(a) Explain why the light does not change direction as it enters the glass block at P.
..................................................................................................................................................................
..................................................................................................................................................................[1]
(b) The light travels in the glass to Q where it strikes the edge of the block at 30° to the normal. The light then emerges into the air.
(i) The refractive index of the glass is 1.5.
Calculate the angle between the normal and the ray in the air after the light emerges from the block at Q.
angle = ..........................................................................[3]
(ii) On Fig. 8.1, sketch the path of the light in the air after it emerges at Q. [1]
(c) The direction of the light striking the curved surface of the glass block is changed. The angle between the ray and the normal at Q gradually increases from 30° to 90°.
Describe what happens to the light that strikes the block at Q as this angle increases.
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.................................................................................................................................................................. [3]

A 12V battery is connected in series to a 24W lamp and to a parallel pair of identical resistors X and Y. Fig. 9.1 is the circuit diagram.

The 24W lamp lights at normal brightness when the potential difference (p.d.) across it is 6.0V.
The lamp is at normal brightness.
(a) Calculate the resistance of the lamp.
resistance = \text{........................}[3]
(b) Determine
(i) the p.d. between A and B,
p.d. = \text{........................}[1]
(ii) the combined resistance of the parallel pair of identical resistors X and Y,
resistance = \text{........................}[1]
(iii) the resistance of X.
resistance = \text{........................}[2]
(c) Resistor X is removed from the circuit in Fig 9.1.
Explain why the lamp becomes dimmer.
\text{.......................................................................}[2]

Fig. 10.1 shows a transformer that consists of two coils P and Q, and an iron core.

There are 200 turns on coil P and 340 turns on coil Q.
A 4.0 V a.c. power supply is connected to coil P.
(a) (i) Explain why there is a voltage between the two terminals of coil Q. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................
[3]
(ii) Explain why the core of the transformer is made of soft iron. ............................................................................................................................ ............................................................................................................................
[1]
(b) (i) Calculate the voltage between the two terminals of coil Q. voltage = ............................................................
[2]
(ii) A heater is connected to coil Q. The current in the heater is 3.5 A. The transformer is 100% efficient. Calculate the current in coil P. current = ............................................................
[2]
(c) A transformer is used to step up the voltage before electrical energy is transmitted over long distances. State and explain one economic effect of transmitting electrical energy at a high voltage. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................
[2]

(a) Fig. 11.1 shows equipment that is used to investigate the effect of a magnetic field on the path of a beam of $\gamma$-rays.



Fig. 11.1

A radioactive source emits $\gamma$-rays. The $\gamma$-rays pass through two small holes in thick lead plates. Then the $\gamma$-rays pass through the shaded region and into the detector.

(i) Suggest the purpose of the two lead plates. [1]

(ii) A magnetic field, directed into the page, is set up in the shaded region.

State and explain what happens to the reading of the detector. [3]

(b) State the relative ionising effects of $\alpha$-particles, $\beta$-particles and $\gamma$-rays. Suggest an explanation for the differences. [3]