Question

A body has a weight 90 kg on the earths surface, the mass of the moon is 1/9 that of the earths mass and its radius is 1/2 that of the earths radius. On the moon the weight of the body is:

• A. 45 kg
• B. 202.5 kg
• C. 90 kg
• D. 40 kg

Answer 1

Answer: (D)

40 kg

Answer 2

Acceleration due to gravity on earth is given by $\frac{m{{\upsilon }^{2}}}{r}=4mg$ $\therefore$ Hence ${{\upsilon }^{2}}=4rg$ $\upsilon =\sqrt{4rg}$ or $\upsilon =\sqrt{4\times 2.5\times 9.8}$ $\upsilon =\sqrt{98}\,\,m/s$ Weight of body on moon $\text{2}0\text{ g }=\text{ 2}\times \text{1}{{0}^{-\text{2}}}\text{ kg},$ $=\frac{360\times 5}{18}=100m/s$