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Homework Help: Centripetal Acceleration

  1. Feb 12, 2009 #1
    A roller coaster at an amusement park has a dip that bottoms out in a vertical circle of radius r. A passenger feels the seat of the car pushing upward on her with a force equal to three times her weight as she goes through the dip. If r = 22.0 m, how fast is the roller coaster traveling at the bottom of the dip?

    At the bottom of the dip, Fn -mg= m(v^2/r). I plugged in 3m for Fn since it's 3 times her weight, and I'm not sure if I'm doing this right.
  2. jcsd
  3. Feb 12, 2009 #2

    Doc Al

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    Staff: Mentor

    Careful. 3m is a mass, not a force. What's her weight? What's 3 times her weight?
  4. Feb 12, 2009 #3
    It looks like everything you have done is correct. When you say that you plugged in 3m for Fn you mean (3m)*g, right? If so, it looks correct.
  5. Feb 12, 2009 #4
    No, I was not using 3mg, just 3m. That's where I messed it up. It makes sense now, thank you so much!
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