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Homework Help: How to calculate critical speed in circular motion?

  1. Apr 13, 2012 #1
    In one textbook, it says that the critical speed is the minimum speed at which an object can complete the circular motion. It gives the formula:
    v = square root of (g*r)
    However, in another textbook it says that the formula is:
    v = square root of (2*g*r)

    How can there be two different types of equation for critical speed? Which one is correct?
    It's funny because they both start off with the same Newton's second law: w+n = mv^2/r

    For the first equation, they said that critical speed occurs when n = 0 whereas for the second equation, they said that critical speed occurs when n = w. Which one is correct?
    Last edited: Apr 14, 2012
  2. jcsd
  3. Apr 15, 2012 #2


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    There may be a typo in the 2nd text book, or perhaps you are reading it out of context.
    Check again.
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