A2 Daily A Level Physics question
An Earth-observation satellite is raised slowly from one stable circular orbit to another with twice the orbital radius, ending in a new stable circular orbit. Ignoring atmospheric drag and mass change, which statement about the new orbit compared with the old one must be true?
Answer
The correct answer is B.
Correct: B — Orbital speed decreases and the satellite’s total mechanical energy increases. A … Higher orbits require lower orbital speed, and raising an orbit requires adding energy (total energy becomes less negative), so both parts are wrong. B … In a larger circular orbit gravity is weaker so the required orbital speed is lower, while the work done to raise the orbit makes the total energy less negative (an increase). C … The orbital speed does decrease, but the total mechanical energy increases because gravitational potential energy increases by more than kinetic energy falls. D … The orbital speed does not increase at larger radius; although total energy increases, pairing it with increasing speed is incorrect.