A communication satellite is moved slowly from a circular orbit of radius about the…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A communication satellite is moved slowly from a circular orbit of radius 4RE about the centre of the Earth to another circular orbit of radius 2RE (RE = radius of the Earth). The firing of on-board thrusters is adjusted so that the speed of the satellite remains practically unchanged during the transfer, that is, any change in kinetic energy may be neglected.
(i) State whether the net work done on the satellite during this transfer is positive, negative or zero. Explain your answer with reference to gravitational potential energy.
(ii) If the same satellite were instead transferred from radius 2RE to 4RE, how would the sign of the work done change? Give reason.
(iii) Draw a qualitative sketch of the magnitude of gravitational force F exerted by the Earth on the satellite versus the distance r from the Earth’s centre. Shade the area that represents the magnitude of the work calculated in part (i).