Physics 9702/42 — October/November 2012

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

questions

100

marks

120

minutes

Topics Magnetic Fields · Communication · Gravitational Fields · Motion in a Circle · Thermodynamics · Ideal Gases · +8 more

Q1Gravitational FieldsMotion in a CircleFree sample

(a)

State Newton’s law of gravitation.

(b)

A satellite of mass $m$ is in a circular orbit of radius $r$ about a planet of mass $M$ .
For this planet, the product $GM$ is $4.00 \times 10^{14}\ \text{N m}^2\ \text{kg}^{-1}$ , where $G$ is the gravitational constant.
The planet may be assumed to be isolated in space.

(i)

By considering the gravitational force on the satellite and the centripetal force, show that the kinetic energy $E_K$ of the satellite is given by the expression

E_K = \frac{GMm}{2r}

(ii)

The satellite has mass $620\ \text{kg}$ and is initially in a circular orbit of radius $7.34 \times 10^6\ \text{m}$ , as illustrated in Fig. 1.1.

Fig. 1.1

Resistive forces cause the satellite to move into a new orbit of radius $7.30 \times 10^6\ \text{m}$ .

Determine, for the satellite, the change in

kinetic energy,

change in kinetic energy = ______ $\text{J}$

gravitational potential energy.

change in potential energy = ______ $\text{J}$

(iii)

Use your answers in (ii) to explain whether the linear speed of the satellite increases, decreases or remains unchanged when the radius of the orbit decreases.

The rest of this paper

11 more questions

Q2Thermodynamics · Ideal Gases7M
Q3Temperature7M
Q4Oscillations9M
Q5Capacitance12M
Q6Magnetic Fields · Electric Fields8M
Q7Magnetic Fields · Alternating Currents9M
Q8Quantum Physics8M
Q9Electronics10M
Q10Medical Physics6M
Q11Communication7M
Q12Communication7M

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