PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A point mass M is fixed in otherwise empty space. Three points P, Q and R lie on the same straight line passing through the mass at distances R, 2R and 3R respectively from the centre of the mass.
(i) State the mathematical expression for the gravitational field strength at a distance r from a point mass.
(ii) If the distance from the mass is doubled, explain quantitatively how the field strength changes. Show the factor by which it increases or decreases.
(iii) Using your result from part (ii), arrange the magnitudes of the field strengths at P, Q and R in descending order and justify your answer.