Cambridge IGCSE Physics - 0625 - Supplement Paper 4 2021 Summer Zone 1

A skydiver of mass 76kg is falling vertically in still air. At time $t = 0$, the skydiver opens his parachute.
Fig. 1.1 is the speed–time graph for the skydiver from $t = 0$.

(a) Using Fig. 1.1, determine:
(i) the deceleration of the skydiver immediately after the parachute opens

deceleration = .............................................................. [2]
(ii) the force due to air resistance acting on the skydiver immediately after the parachute opens.

force = ............................................................. [3]
(b) Explain, in terms of the forces acting on the skydiver, his motion between $t = 0$ and $t = 6.0$ s.

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(c) Explain why opening the parachute cannot reduce the speed of the skydiver to zero.

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Fig. 2.1 shows a wooden trolley of mass 1.2kg at rest on the rough surface of a bench.

A ball of mass 0.52g travels horizontally towards the trolley. The ball embeds itself in the wood of the trolley. The trolley moves with an initial speed of 0.065m/s.

(a) Calculate:

(i) the impulse exerted on the trolley

impulse = .............................................................. [2]

(ii) the speed of the ball as it hits the trolley.

speed = .......................................................... [2]

(b) As the trolley moves across the rough surface, it slows down and stops.

Explain, in terms of the work done, the energy change that takes place as the trolley slows down.
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[Total: 7]

(a) Explain, in terms of molecules, why liquids are very difficult to compress.

(b) Fig. 3.1 shows a device that uses liquid pressure to lift heavy boxes.

The boxes are lifted by pumping oil into the cylinder.

The force upwards on the piston due to the oil, and the force downwards on the piston due to the air above the piston, combine to produce a constant force of 8800 N.

The pressure of the air is $1.0 \times 10^5 \text{Pa}$ and the cross-sectional area of the bottom surface of the piston is $0.016 \text{m}^2$.

(i) Calculate the pressure of the oil at the bottom surface of the piston.

(ii) As the boxes are lifted, the depth of the oil increases. Explain why the pump must exert an increasing pressure on the oil as the depth of the oil increases.

(iii) Suggest one reason why the force of 8800 N in (b) cannot lift boxes of weight 8800 N.

An aluminium saucepan with a plastic handle contains cold water.

Fig. 4.1 shows the saucepan on a hotplate.



(a) State why the pan is made from aluminium but the handle is made from plastic.

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(b) The hotplate is switched on and, as the temperature of the water increases, the internal energy of the water increases.

(i) State, in terms of molecules, what is meant by an increase in internal energy.

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(ii) Explain, in terms of the atomic lattice and electrons, how thermal energy is transferred through the aluminium.

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(iii) Eventually, the water reaches boiling point. Thermal energy from the hotplate is still being transferred to the water.

Explain, in terms of molecules, the effect of this thermal energy on the water.

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(iv) The mass of the water decreases by 0.11 kg in 300 s. The specific latent heat of vaporisation of water is $2.3 \times 10^6$ J/kg.

Calculate the rate at which the water gains thermal energy.

rate of gain of energy = ............................. [3]

[Total: 11]

Fig. 5.1 shows the structure of a liquid-in-glass thermometer.

The bulb of the thermometer is placed into a beaker of warm water. As the liquid expands, it moves along the tube.
(a) Explain, in terms of molecules, why a liquid expands when heated.
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(b) Explain, in terms of molecules, why a liquid expands more than a solid when heated.
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(c) A second thermometer has a larger bulb that contains more of the same liquid than the thermometer shown in Fig. 5.1. It has a different scale. In every other way, it is identical.
(i) Explain how the sensitivity of the second thermometer compares with the sensitivity of the thermometer in Fig. 5.1.
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(ii) Explain how the range of the second thermometer compares with the range of the thermometer in Fig. 5.1.
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(d) (i) State one everyday problem that is a result of thermal expansion.
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(ii) Suggest and explain one way of solving this problem.
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Fig. 6.1 is a full-scale diagram that represents a sound wave travelling in air.



(a) On Fig. 6.1, mark two points, each at the centre of a different compression. Label both of the points C. [1]

(b) The speed of sound in air is 330 m/s. Measure the diagram and determine the frequency of the sound.

frequency = ........................................................... [3]

(c) The wave reaches a barrier. Fig. 6.2 shows the wave passing through a gap in the barrier.



The frequency of the wave is increased to a value many times greater than the value obtained in (b).

Describe and explain two ways in which a diagram representing the wave with the greater frequency differs from Fig. 6.2.

1. .................................................................................................................................
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2. .................................................................................................................................
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[Total: 7]

Fig. 7.1 represents an alternating current (a.c.) generator.

(a) A student rotates the handle H, as shown in Fig. 7.1.
(i) On Fig. 7.2, sketch a graph to show how the electromotive force (e.m.f.) between terminals X and Y varies with time during two complete revolutions of the coil.

[3]
(ii) On Fig. 7.2, mark and label a point P, for the e.m.f. when the coil is horizontal, as shown in Fig. 7.1.
[1]
(iii) The student turns the handle more quickly.
State two ways in which the e.m.f. between terminals X and Y changes.
1. ..........................................................................................................................................................
2. ..........................................................................................................................................................
[2]
(b) Terminals X and Y are connected to the primary coil of a transformer.
State and explain what happens in the transformer as the student turns the handle of the a.c. generator.
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[3]
(c) Explain why the power losses in transmission cables are lower when electrical energy is transmitted at higher voltages.
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[2]

A student sets up a circuit that includes a 12V battery, an 800Ω resistor, a voltmeter and a thermistor. Fig. 8.1 is an incomplete circuit diagram because the symbol for the thermistor is missing.

The thermistor is connected between terminals P and Q.
(a) Complete Fig. 8.1 by drawing the symbol for a thermistor between terminals P and Q. [1]
(b) The 12V battery consists of eight identical cells connected in series. Calculate the electromotive force (e.m.f.) of each cell.
e.m.f. = .............................................................. [1]
(c) The reading on the voltmeter is 8.0V.
(i) Determine the resistance of the thermistor.
resistance = .............................................................. [3]
(ii) A few hours later, the student notices that the reading on the voltmeter is greater. Explain what can be deduced from this observation. [3]

There are three naturally occurring isotopes of hydrogen: hydrogen-1, hydrogen-2 and hydrogen-3. The nuclide notation for hydrogen-1 is $^1_1\text{H}$.
(a) Write down the symbol, using nuclide notation, for:
hydrogen-2 .................................
hydrogen-3 .................................
[1]
(b) In a fusion reactor, a nucleus of hydrogen-2 and a nucleus of hydrogen-3 undergo fusion.
(i) State what is meant by nuclear fusion.
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[2]
(ii) The fusion reaction produces a free neutron and \textit{one} other particle.
Write down, using nuclide notation, the equation that represents this reaction.
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[3]
(c) Nuclear fusion in the Sun is the source of most but not all of the resources that are used to generate electrical energy on Earth.
State \textit{two} resources for which nuclear fusion in the Sun is \textit{not} the source.
1. ..............................................................................................................................
2. ..............................................................................................................................
[2]
[Total: 8]