Do you weigh less at the equator than at the poles?

13 January 2008

Question

Do you weigh less at the equator than at the poles because of centrifugal force on the rotating Earth?

Answer

Yes, you do weigh a bit less at the equator than at the poles.

Although your mass is the same, so that you've got the same amount of fat - the same amount of "you", when you're at the equator you're spinning round so you're getting thrown away from the Earth due to the centrifugal force (the same force you've experienced if you've ever sat on a roundabout and, when it spins around, you can feel yourself being pushed away from the centre).

And, in fact, you're actually lighter than even the centrifugal force can account for, because the Earth "bulges out" at the equator, so you're further from the centre of the Earth. Since gravity acts through a body's center of mass, the further you are from the centre the weaker the gravitational acceleration you will feel, because gravity weakens over distance.

So even if the Earth wasn't spinning, you're actually lighter at the equator than you'd be at the poles.

Comments

More mass=more gravity.... If it bulges at the center the gravity is greatest at the center. But the effects would theoretically be slightly offset but the centrifugal momentum. If this is true or to what degree i don't know.

Please read the answer supplied above again.

The Earth bulges at the equator, meaning that a body standing on the equator is further from the planet's centre of mass than at the poles. Since gravity decays according to an inverse square law, the greater distance to the equator from the Earth's centre means that you will weigh a subtly lesser amount than you would at the North or South Pole.

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