Question

the ratio of work done to lift a mass of 2 kg to the height 2m from a planet having mass 4 times and radius equal to that of the earth is, when compared to earth a) 4:1 b)1:4 c) 2:1 d) 1:2​

Answer 1

Explanation:

Work done On Earth = mgh

g = GM/r^2 ( here , M is the mass of the Earth )

Work = 2 × Gm/r^2 × 2 = 4 Gm/r^2 joules

Now , g of planet = 4 GM / r^2

Work done on Planet = mgh

Work = 2 × 4 GM / r^2 × 2 = 8 GM / r^2 joules.

Work on planet / Work on Earth = 8 GM / r^2 × r^2 / 4 GM

= 2 : 1

Therefore, it it is your answer.

I hope it helps you. If you have any doubts, then don't hesitate to ask.