Question

1) A body weighs 30 kg on the surface of the earth. How much would it weigh on the surface of the planet whose mass is 1/9 the mass of the earth and radius is half that of earth.

Answer 1

1/9x30=10/3=3.3333.

Answer 2

Gravity = G × (m1 × m2)/d^2
Weight of the body on earth = 30 Kg
Mass of the body =3 Kg
Mass of earth = 6 × 10^24 Kg
Mass of the planet = 2/3 × 10^24Kg
Radius of earth = 6.4 × 10^3 Km
Radius of the planet = 3.2 × 10^3 Km
Thus gravitational force =
6.67 × 10^-11× (2/3×10^24 ×3)/3.2×10^3
=0.41 × 10^8 N
Hence weight of the body on that planet
=Mass × g = 3 ×0.41×10^8= 1.23×10^8