An object of mass is to be moved slowly from a point that is at a distance from the…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
An object of mass 50kg is to be moved slowly from a point that is at a distance 2R from the centre of the Earth to another point at a distance 4R (both distances measured from the Earth’s centre). Assume the Earth’s mass is 6.0×1024kg and its radius is R=6.4×106m.
(a) Find the gravitational potential difference between the two points.
(b) Calculate the work that must be done by an external agent in moving the object between these points.
(c) Express the work obtained in part (b) in both megajoules (MJ) and kilojoules per kilogram (kJ kg−1).
(d) State whether the work done by the external agent is positive or negative and give a brief justification.