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9702/42

Physics 9702/42 — May/June 2022

Cambridge A-Level · A Level Structured Questions · worked solutions for every part, with the mark scheme

10
questions
100
marks
120
minutes

Topics Nuclear Physics · Magnetic Fields · Gravitational Fields · Electric Fields · Motion in a Circle · Medical Physics · +7 more

Q1Gravitational FieldsFree sample
(a)
(i)

Define gravitational potential at a point.

2M
(ii)

Starting from the equation for the gravitational potential due to a point mass, show that the gravitational potential energy EPE_P of a point mass mm at a distance rr from another point mass MM is given by

EP=−GMmrE_P = - \frac{GMm}{r}

where GG is the gravitational constant.

1M
(b)

Fig. 1.1 shows the path of a comet of mass 2.20×1014 kg2.20 \times 10^{14}\ \text{kg} as it passes around a star of mass 1.99×1030 kg1.99 \times 10^{30}\ \text{kg}.

At point X, the comet is 8.44×1011 m8.44 \times 10^{11}\ \text{m} from the centre of the star and is moving at a speed of 34.1 km s−134.1\ \text{km s}^{-1}.

At point Y, the comet passes its point of closest approach to the star. At this point, the comet is a distance of 6.38×1010 m6.38 \times 10^{10}\ \text{m} from the centre of the star.

Both the comet and the star can be considered as point masses at their centres.

(i)

Calculate the magnitude of the change in the gravitational potential energy ΔEP\Delta E_P of the comet as it moves from position X to position Y.

ΔEP\Delta E_P = ______ J\text{J}

2M
(ii)

State, with a reason, whether the change in gravitational potential energy in (b)(i) is an increase or a decrease.

1M
(iii)

Use your answer in (b)(i) to determine the speed, in km s−1\text{km s}^{-1}, of the comet at point Y.

speed = ______ km s−1\text{km s}^{-1}

3M
(c)

A second comet passes point X with the same speed as the comet in (b) and travelling in the same direction. This comet is gradually losing mass. The mass of this comet when it passes point X is the same as the mass of the comet in (b).

Suggest, with a reason, how the path of the second comet compares with the path shown in Fig. 1.1.

1M

The rest of this paper

9 more questions
  • Q2Electric Fields · Motion in a Circle · Nuclear Physics · Medical Physics13M
  • Q3Temperature · Ideal Gases · Thermodynamics12M
  • Q4Oscillations8M
  • Q5Capacitance11M
  • Q6Magnetic Fields10M
  • Q7Magnetic Fields10M
  • Q8Quantum Physics8M
  • Q9Astronomy and Cosmology7M
  • Q10Nuclear Physics11M
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