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Homework Help: Ap answer? for gravity question

  1. Jan 20, 2009 #1
    Looking at an old AP multiple choice test, I found this question and answer:
    A satellite of mass M moves in a circular orbit of radius R at a constant speed v. Which of the following must be true?

    One of their "true" answers states: The net force on the satellite is equal to MR and is directed toward the center of the orbit.

    Can anyone show me the math to show this. I'm sure I'm missing something obvious.

  2. jcsd
  3. Jan 20, 2009 #2
    "MR" is not a force, as the units don't match. The quantity "M*v^2/R-" is force (centripetal).

  4. Jan 20, 2009 #3
    That's what I thought, too. AP is famous for their typos on the Physics test. I'm guessing this is one of them.
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