The value of acceleration due to gravity at a depth of $ 1600 \,km $ is equal to: (Radius of Earth $ = 6400 \,km $) (in $\,ms^{-2}$)

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: If we move from poles to equator,the direction of acceleration due to gravity of earth always points towards the center of earth without any variation in its magnitude.
Reason $R$: At equator,the direction of acceleration due to the gravity is towards the center of earth. In the light of above statements,choose the correct answer from the options given below.

At a height of $h$ $km$ from the surface of the Earth,the gravitational potential and the value of $g$ are $-5.4 \times 10^7\, J kg^{-1}$ and $6.0\, m s^{-2}$ respectively. Take the radius of the Earth as $6400\, km$.

If $M$ is the mass of the Earth and $R$ is its radius,the ratio of the gravitational acceleration $g$ to the gravitational constant $G$ is:

The time period of a simple pendulum increases by a factor of $\sqrt{2}$ at a height $h$ from the surface of the Earth. Then the value of $h$ is:

Weight of a body is maximum at