# Gravitational Acceleration

• Milind_shyani

#### Milind_shyani

hello
The gravitational acceleration at the equator is the least and at the pole is the maximum due to the rotation of the Earth on its axis.Why?

The Earth is not precisely spherical, it is flattened at the poles because of the Earth's rotation. This is simply because of the centrifugal force, objects at the equator have the greatest distance from the axis of rotation so are 'flung outwards' more than at the poles. So at the poles you are closer to the center of the Earth and experience a greater gravitational acceleration.

It should be borne in mind that "g" is generally meant to mean "effective gravitational acceleration" and includes the effects of a rotating Earth (which predicts a lower g at equator than by the poles), the deviatioric correction due to the non-spherical form of the Earth, as the two main correctional effects.

Galileo is right - the oblateness of the Earth is the biggest factor in the difference in gravitational attraction.

However, the way the question is worded, I think it's addressing centripetal acceleration. Which point will have a larger linear velocity due to the rotation of the Earth: a point on the equator or a point on one of the poles?

Both the oblateness of the Earth and centripetal force contribute to reducing the net force, and the resulting acceleration, at the equator (with oblateness having nearly twice as much affect).

I never said that Galileo was wrong..

arildno said:
I never said that Galileo was wrong..
$$g_{a} = g - r\omega^2\cos^2\theta$$
where $g_{a}$ is the apparent force of gravity and $\theta$ is latitude. This assumes the Earth is spherical, but is a good approximation for a non-spherical earth.