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Homework Help: Understanding of rotational motion

  1. Dec 2, 2003 #1
    Hello anyone that can help. I am trying to gain an understanding of rotational motion, including (tangential speed, angular momentum, centripetal force and so on). The first question I was hoping that someone could help me is:

    An automobile speedometer is configured yo read speed proportional to the rotational speed of its wheels. If larger wheels are used, will the speedometer reading be higher, lower or the same.

    I understand the question but I was hoping someone could help explain this to me in a mathamatical equation.

    Thank you for your help. I promise not to bug you guys to much!
  2. jcsd
  3. Dec 2, 2003 #2
    The question is slightly ill-posed, since it didn't specify what is kept the same when the wheels are changed. But I assume they mean that the ground speed of the automobile is kept the same. The ground speed is the same as the tangential speed v of a point on the wheel. By [itex]v = R\omega[/itex], the rotational speed ω must decrease if R increases, if we hold v constant.
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