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Homework Help: Total Upward force

  1. Jan 14, 2010 #1
    skateboard mass = 65kg

    he skates down on a half pipe, radius = 3m

    If he is travelling at 3.6 m/s when at bottom of ht hallf pipe, what will be the total upward force?

    Is this basically the centripetal force + the reaction to the weight?

    i.e. centripetal force + mg?
  2. jcsd
  3. Jan 14, 2010 #2

    Doc Al

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    Staff: Mentor

    The phrase 'total upward force' is a bit ambiguous, as is the term 'reaction to the weight'. Presumably you want the upward force that the surface exerts on the skater (usually called the 'normal force', N).

    If so, you have the right answer. But a simpler way to understand it is to apply Newton's 2nd law:
    ΣF = ma
    N - mg = mac
    Thus: N = mac + mg
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