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Compare weights at equator and poles?

  1. Oct 12, 2013 #1

    I need some help understanding this question.
    If we take a mass of a person as 100kg, what would he weigh at the poles and the equator, in Newtons? How do I do this please?

    Thanks and much appreciate some help.
  2. jcsd
  3. Oct 12, 2013 #2


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  4. Oct 12, 2013 #3


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    The first thing you should think about is exactly what you mean by "weight"! Do you mean "what a spring scale would show if the person were to stand on it"? In that case you could, treating the earth as a sphere, use "mg" but allow for the "centrifugal force" effect.

    Taking the "squashed" shape of the earth into effect, as mathman suggests, would be more accurate but much harder, requiring you to use "F= -(Gmm)/r^2" with different values for the distance from the center of the earth to the pole and from the center of the earth to the equator. And, of course, you should still allow for the apparent reduction in force due to the rotation of the earth.
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