Question

If a planet existed whose mass was twice that of the earth and whose radius 3 times greater,How much will a 1kg mass weigh on the planet ?

Answer 1

For earth,

Mass of earth = M

Radius of earth = R

Mass of the body = m = 1 kg

Weight on earth is, We = GMm/R2 = mg

For the other planet,

Mass = 2M

Radius = 3R

So, weight is, Wp = G(2M)(m)/(3R)2

=> Wp = (2/9)(GMm/R2)

=> Wp = (2/9)(mg)

=> Wp = (2/9)(1 × 9.8)

=> Wp = 2.18 N

Mass of the body remains same (1 kg), the weight of the body in the planet is 2.18 N.