Question

A body weighs $700$ gm.wt on the surface of the earth. How much will it weigh on the surface of a planet whose mass is ${\left(\frac{1}{7}\right)}^{th}$ of mass of earth and radius is half of that of the earth.

• A. $200$ gm.wt
• B. $400$ gm.wt
• C. $50$ gm.wt
• D. $300$ gm.wt

Answer 1

The correct option is B $400$ gm.wt

We know that $g=\frac{GM}{R^2}$
On the planet , $g_P=\frac{\frac{GM}{7}}{\frac{R^2}{4}}=\frac{4g}{7}=\frac{4}{7}g$
Hence, weight on the planet.
$=700\times \frac{4}{7}=400\text{gm.wt}$