Final answer:
The difference in the value of gravitational acceleration ('g') at the equator compared to the poles is because of Earth's oblate spheroidal shape and the effect of centripetal force due to Earth's rotation, which both cause 'g' to be slightly less at the equator.
Step-by-step explanation:
The Variations in the Value of 'g' from Equator to Poles
The value of "g," or gravitational acceleration, is different at the equator compared to the poles. One reason is that Earth is not a perfect sphere—instead, it's an oblate spheroid, which means it is slightly flattened at the poles and bulges at the equator. This bulge at the equator means that the radius of Earth is about 30 km greater there than at the poles. Consequently, if you're standing at the equator, you're slightly further away from the center of the Earth, and since gravitational force decreases with distance, the value of 'g' is less at the equator.
Additionally, the rotation of Earth causes a centripetal force which acts away from the axis of rotation. At the poles, the centripetal acceleration is virtually zero, since they are on the rotation axis. However, at the equator, this force is maximal due to the larger radius of Earth's rotation there. Since the centripetal force is directed away from the Earth, it reduces the overall effect of gravity, making 'g' smaller at the equator than at the poles.