Question

The radius of earth is about 6400 km and that ofmars is 3200 km. The mass of the earth is 10 times the mass of mars. An object weight 200 N on the surface of earth. Its weight on the surface of mars will be.

• A. 80 N
• B. 40 N
• C. 20 N
• D. 8 N

Answer 1

The correct option is A 80 N

At surface of earth, $mg{R}_e^2=G{M}_{e}m$

At surface of mars, $m{g}^{\prime }{R}_m^2=G{M}_{m}m$

Thus $\frac{W_m{R}_m^2}{W_e{R}_e^2}=\frac{M_m}{M_e}$

$\frac{W_m(3200{)}^2}{200\left(6400\right)2}=\frac{M_m}{10M_m}$

$⟹W_m=80N$