Do you weigh less at the equator than at the poles?
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
Don't agree
Hi,
We had this question at a pub quiz this week. I don't agree that the gravitational force at the equator is less. Let's ignore rotation for a second. Your "further from the centre of mass" argument would only hold true if the earth were a perfect sphere in which case you could assume that all the mass is at the centre of the earth. But it isn't. It is flattened. So this assumption is invalid. Consider if the earth was shaped like a pizza. Where would you experience greatest force? if you stand at the centre or if you stand on the edge? In both cases, assuming you stand perpendicular to the surface, when you stand at the centre most of the mass is to your left, right, in front, behind. Very little is below your feet. On the edge on the other hand, almost all the mass of the pizza earth is below your feet. The force would be significantly greater. The earth is a very fat pizza, so why do you say for force of gravity is greater at the pole? What you need to do for any irregular body is to integrate the force over the entire body mass. When you stand at the equator there is a part of the earth directly below your feet, as there is when you stand at the pole. This block of mass exerts exactly the same force as it does at the pole, you are not any further away from it. Integrate the effect over the entire earth. More mass below you = more gravity.
Nope.
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.
Sorry, Danny, I don't agree
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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