Question

: A planet whose size is same and 4 times as that of earth. Find the amount of energy needed to lift a 2 kg mass vertically upward through 2m distance on the planet. The value of g on the surface of earth is 10 m/sec2?

Answer 1

The acceleration due to gravity is given by g= GM/R^2. So in the other planet acceleration due to gravity is given by g'= G4M/R^2 = 4 GM/R^2 = 4g

So energy to lift 2kg mass to 2m height is given by

Ep = mg'h = 2x4gx2 = 2x4x10x2 = 160J