12: Exam Questions

Question 1

Shade the area on the graph that shows the Gravitational Potential at distance D from the centre.

Answer 1

From D, between the x-axis and the curve, into the asymptote. To the right

Question 2

Explain why the centripetal acceleration of the moon in orbit is equal to the gravitational field strength of the earth at that distance

Answer 2

centripetal force = gravitational force; mass * acceleration = mass * field strength (cancel out masses);

Question 3

Calculate the speed of the moon using the centripetal acceleration. Distance to moon: 3.8*10^8 m

Answer 3

(g=) v^2/r = GM/r^2

Question 4

Explain why the gravitational force of a planet does not effect the speed of an orbiting satellite

Answer 4

force at right angles to velocity/motion; so no work done/energy transferred;

Question 5

Explain why the space vehicle remains on the surface of the asteroid despite the rotation of the astroid (1)

Answer 5

Centripetal force less than weight of vehicle

Question 6

It is suggested that a less massive space vehicle would be less likely to remain on the surface of the astroid. Comment on this suggestion. (2)

Answer 6

There would be no effect (on the vehicles likelihood of staying on the surface)
Centripetal force: weight ratio is independent of mass

Question 7

Explain why a satellite moves at constant speed even though it is accelerating (2)

Answer 7

There is no force in the direction of motion
So no linear acceleration. However, the velocity is changing because the direction of motion is changing. Acceleration is the rate of change of velocity