A student claims that no external work is needed to move a object slowly from the…
PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A student claims that no external work is needed to move a 1kg object slowly from the Earth’s surface to a point at a distance 2R⊕ from the Earth’s centre, because the gravitational force decreases with distance.
(i) Explain qualitatively why this claim is incorrect.
(ii) Starting from the definition of gravitational potential energy, evaluate the sign and relative magnitude of the change in potential energy for the transfer described. State clearly whether the external agent must supply energy or whether energy is released.