The radius of Earth is about $6400 \,km$ and that of Mars is $3200 \,km$,and the mass of the Earth is about $10$ times the mass of Mars. An object weighs $200 \,N$ on the surface of Earth. Then,its weight on the surface of Mars will be (in $\,N$)

Suppose that the angular velocity of rotation of the earth is increased. Then,as a consequence:

Choose the correct alternative:
$(a)$ Acceleration due to gravity increases/decreases with increasing altitude.
$(b)$ Acceleration due to gravity increases/decreases with increasing depth (assume the Earth to be a sphere of uniform density).
$(c)$ Acceleration due to gravity is independent of mass of the Earth/mass of the body.
$(d)$ The formula $-G M m(1 / r_{2}-1 / r_{1})$ is more/less accurate than the formula $m g(r_{2}-r_{1})$ for the difference of potential energy between two points $r_{2}$ and $r_{1}$ distance away from the centre of the Earth.

The weight of a body at the surface of earth is $18 \, N$. The weight of the body at an altitude of $3200 \, km$ above the earth's surface is $........ \, N$ (given,radius of earth $R_e = 6400 \, km$).

If the earth suddenly shrinks (without changing mass) to half of its present radius,the acceleration due to gravity will be

$A$ planet has the same density as that of the Earth,and the universal gravitational constant $G$ is twice that of the Earth. The ratio of the acceleration due to gravity on the planet to that on the Earth is: