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Homework Help: Force Diagram

  1. Jun 11, 2008 #1
    (a) Assume that the Earth is a uniform sphere with a radius r which rotates such that the speed of the ground at the equator is v which is constant.

    (i) Draw a diagram showing the forces acting on a person standing on the equator.

    There would be the following forces acting on the person:

    Gravity (mg)
    Normal (-mg)
    Friction at the point of contact to the earth
    Centripetal force (?)

    (ii) Explain why a person in this situation must experience a net force even though their speed is constant.

    Does this have to do with the centripetal force? So they need to have a net force towards the center of the earth??

    Any help with these would be greatly appreciated.
  2. jcsd
  3. Jun 11, 2008 #2


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    Science Advisor
    Homework Helper

    Since you are talking about force diagrams, I assume you know about vectors. In (ii) the question says that [itex]|\vec v|[/itex] is constant, but is [itex]\vec v[/itex] constant as well?
  4. Jun 11, 2008 #3
    so the magnitude of v is constant but the direction is changing hence you are accelerating and if you are accelerating your are experiencing a net force?
  5. Jun 11, 2008 #4

    Doc Al

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    Staff: Mentor

    Absolutely. So redo your analysis of the forces acting on the person.
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