Question

Imagine a new planet having the same density as that of earth but it is 3 times bigger than the earth in its size. If the acceleration due to gravity on the surface of the earth is g and that on the surface of the new planet g^‘ is?

(a) g^‘=g/9

(b) g^‘=27g

(c) g^‘=9g

(d) g^‘=3g

This question was addressed to me in an international level competition.

My question comes from Weight of a Body topic in portion Mechanical Properties of Solids of Engineering Physics I

Answer 1

Correct choice is (d) g^‘=3g

Explanation: g=4/3 πG^Rp

g^‘=4/3 πG^Rp ρ=4/3 πG×3R×ρ

g^‘=3g.