**Variation of Acceleration due to Gravity**

We have learnt from the law of gravitation that the value of acceleration due to gravity (g) does not depend on the mass (m) of the body. Value of g depends on the distance of the point from the centre of the earth. From this we can conclude that at a particular position of the earth’s surface value g remains constant, but varies with different locations. Consider the deviation of g when a body moves distance upward or downward from the surface of earth. Let g be the value of acceleration due to gravity at the surface of earth and g’ at a height h above the surface of earth.

Taking mass of the Earth, M = 5.983 x 10^{24} and Radius, R = 6.36 x 10^{6} m, value of g on Earth’s surface,

g = [(6.657 x 10^{-11} Nm^{2}kg^{-2}) x (5.983 x 10^{24} kg) / (6.36 x 10^{6} m)]

= 9.8465 ms^{-2}

On the surface of the earth value of g is more. Again at the equator its value is more than that at the poles. It is zero at the centre of the earth.