Gravitation

Gravitational constant is equal in magnitude to that force of attraction which acts between two particles each of unit mass separated by a unit distance apart.

(Newtons law of gravitation) where
and are masses, r is the distance between them, and F is force.
Dimensions of gravitational constant

When earth moves round the sun then according to Keplers second law, the radius vector drawn from the sun to earth, sweeps out equal areas in equal time, i. e., its areal velocity (or the area swept out by it per unit time) is constant. While in such motion, angular velocity, kinetic energy and potential energy change.

The value of acceleration due to gravity at a height above the surface of the earth is given by

where is radius of earth. When li is negligible compared to , we have

Given



Note : The value of acceleration due to gravity decreases on going above or below the surface of earth.

Acceleration due to gravity decreases both at altitude and depth.
If is the acceleration due to gravity at a point, at a height h above the surface of earth, and be acceleration due to gravity on earths surface, then

If '' be the acceleration due to gravity at a point at depth , below the surface of earth, then

But (given)



Note The value of acceleration due to gravity, also decreases due to rotation of earth.