Question

The Weight of an object varies inversely as the square of its distance from the centre of the earth.the weight of a spacecraft is observed to be only a quater of its weight on earth.How far is the spacecraft from the surface of the earth?
[take radius of the earth to be 6400km ]

Answer 1

since the weight varies as 1/d^2, if its weight is 1/4 as much, d is twice as big.

That is, 1/(2d)^2 = 1/4 * 1/d^2