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Homework Help: Static Friction Question

  1. Jan 30, 2005 #1
    I had a questiion about static friction.

    Basically, if the gravitational acceleration on the moon is 1.63m/s^2, and your weight is roughly 1/6 of that on Earth, you can jump higher on the moon than you can on earth.

    So if you were playing basketball on the moon, you could jump higher and score easier. However, how would this 1/6 of gravity and 1.63m/s^2 gravitational constnat affect how fast you speed up and slow down running on the basketball court on the moon?

    An example I'm attempting to use is that speed is 5m/s to the right, then you slow down and want to run at 5m/s to the left. Could this be done faster on the moon or on the earth? And how does this relate to the concepts of static friction and the maximum static friction value.

    Any help that could be given would greatly be appreciated.
  2. jcsd
  3. Jan 30, 2005 #2
    some hints:
    How does static friction help us move? Think of what happens when you walk on ice?
    What force(s) does static friction depend on? How is this force affected by gravity?
    (It may help to look at a Free-Body-Diagram for a runner)

    If this doesn't help, come back.
  4. Jan 30, 2005 #3

    Andrew Mason

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    The static friction force just has to be sufficient to give you an impulse of [itex]m\Delta v[/itex] where m is your mass (not your weight) and [itex]\Delta v[/itex] = 10 m/s. If your mass is 80 kg and you want to do this move in 1 second, the friction force has to be [itex]F = m\Delta v/t = 80*10/1 = 800 N[/itex]. This is the same whether you are on the earth or the moon.

    The friction force would be [itex]F_f = \mu_s mg[/itex]. Since g would be 1/6 of that on the earth, you would need to make sure that your shoes and the basketball court floor provided a coefficient of friction of about 6 in order to do this move. On earth, the friction coefficient need only be about 1. But that's ok. Just think of the slam dunks and jump shots you could do.

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