Question

A body weight $700N$ on the surface of the earth. What is its weight on the surface of a planet whose mass is $1/7th$ of that of earth and radius is $1/2$ times that of earth?

• A. $400N$
• B. $300N$
• C. $700N$
• D. $500N$

Answer 1

The correct option is A $400N$

The gravitational acceleration on earth's surface is $g=\frac{GM}{R^2}$

For planet, $M_p=M/7$ and $R_p=R/2$

So, $g_p=\frac{G{M}_p}{R_p^2}=\frac{G\left(M/7\right)}{(R/2{)}^2}=\frac{4}{7}g$

Thus, weight of the body on planet's surface $=700g_p=700\left(4/7\right)=400N$