**Variation of g-variation of acceleration due to gravity**

We know that the force of gravity varies from place to place on the surface of earth.

There are two reasons behind this variation:

- The shape of earth.
- The rotation of earth.

The earth is not a perfect sphere, but bulges at the equator. Therefore, if a body is taken from pole to the equator its distance from the centre of the earth will change. Consequently, the gravitational force also varies.

**Variation of g with altitude**

Consider the variation 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.

If the earth is considered as a sphere of homogeneous composition, then **g** at any point on the surface of the earth is given by:

This expression indicates that the acceleration due to gravity decreases with altitude.

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