Question

A large ball of steel has a mass of 500 kg. A smaller ball of steel of mass of 75 kg is placed some distance from the larger ball. The force of gravitation between them is given by F = GMm/r2
Compare, as a ratio, the force of gravity between the balls when they are placed 15 m apart and 20 m apart.
A) 9/16
B) 16/9
C) 4/3
D) 3/4

Answer 1

Force between the balls is: at 15 m : F(15) = G*500*75/15^2 = G*37500/225 at 20 m : F(20) = G*500*75/20^2 = G*37500/400 Then the ratio will be F(15)/F(20) = (G*37500/225)/(G*37500/400) = 400/225 = 16/9 Solution: Ratio is B) 16/9