Question

A solid lead sphere of radius 10 m (about 66 feet across!) has a mass of about 57 million kg. If two of these spheres are floating right next to each other (centers 20 m apart) in deep space, the gravitational attraction between the spheres is only 540 N (about 100 pounds). How large would this gravitational force be if the distance between the centers of the two spheres were doubled?

Answer 1

here,

mass , m = 57 Mkg

radius of the lead sphere , r = 10 m

distance between the sphere , d = 20 m

force when d= 20 m , F = 540 N

when dnew = 2 * d

dnew = 40 m

let the new force be Fnew

using gravitation law

Fnew / F = (d/dnew)^2

Fnew = 540 * (20/40)^2

Fnew = 135 N

gravitational force when the distance between the centers of the two spheres is doubled is 135 N