### Re: gravity vs centripetal force @ equator vs poles

Area: Physics
Posted By: James Cross, Undergraduate Electronics/Electrical Engineering, Birmingham University
Date: Thu Feb 20 03:52:50 1997
Message ID: 855511961.Ph

Your assumption is correct, if the Earth were spherical your weight would be altered
if you step on scales at the poles than at the equator.  Unfortunatley this effect is almost
cancelled out by the fact that the earth was distorted by its own spinning action
and so this lessens the effect because there is more earth under you at the equator
than there is at the poles.  This effect makes the difference less noticable but
you will still weigh less on the pole.  The difference?  Well g is taken to be an average
9.80665 and differs by about .1 so you could be about 50-100grams different.

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Ross Lee Graham, PhD adds the following:

A reference weight has not been given here. For the values Mr. Cross gives, if you weigh 100 kilograms at the poles you would weigh in at about 99 at the equator, which is about one percent difference (a lot more than 50 grams). However, using values for g measured by the Russians:
g at the equator is given as 9.78038 m/s2
g at the poles is given as 9.83210 m/s2
The difference is 0.1283 etc.

I leave the arithmetic to you.

Second, if the Earth is fatter at the equator it also undergoes a higher centripetal force.

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