Why does the Earth bulge around the equator? This is not a question about tides

Question

Why does the Earth bulge around the equator? This is not a question about tides but rather has more to do with centripetal forces.. Look at the question 6 above. You are on a ride called Gravitron. It is essentially a rotating cylinder. At a certain race of rotation the floor drops our from under you and you stay stuck to the wall. Draw a free body diagram for this situation and (thus is a big one), explain how each force in your diagram effects your motion. Suppose you are experiencing a centripetal of 1200 N and the ride has a radius of 5 m. What is your speed if you have a mass of 65 kg. Imagine that the wall behind you is actually a large scale. Describe what happens to the weight registered on the scale if the ride is run at a greater speed.

Explanation / Answer

The difference between the polar and equitorial diameter of a planet created due to centrifugal force of rotation of the planet is called equatorial bulge. Our Earth also has an equatorial bulge which is about 42.77 km. It means that the diameter along the equatorial plane is 42.77 km greater than the diameter measured along the poles.

The value of the radius of Earth is calculated by the average of these two radii (equatorial and polar).

It can be better explained by centripetal force. The centripetal force on the rotating boby is given by;

F=Mv2/R

Here,

M=mass of rotating body

V=velocity of rotating body

R=distance of rotating body from the axis of rotation.

Considering Earth as the rotating disc, we find that mass and distance (R) are very small at the poles. However, the Mass increases significantly as we move towards the equator as compared to distance (R) as the core of the Earth is also considered in the cross sectional disc around the equator. Thus, density along the equator is higher then the density at the poles.It results in higher centripetal force at the equator than at the pole. this centripetal force is balanced by an equal amount of centrifugal force. the equator has high water envelop surrounding it. water being a fluid,the high centrifugal force at the equator results in bulge in water envelops.

Therefore, the bulge in Earth surface is result of centrifugal/centripetal forces.

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