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Uniform circular motion

  1. Oct 31, 2016 #1
    :H:H:H1. The problem statement, all variables and given/known data

    2. Relevant equations
    equations is not needed here
    3. The attempt at a solution
    I have no idea :(
    Please help me!!
  2. jcsd
  3. Nov 1, 2016 #2
    They are asking which shadow is moving the fastest on the ground. What direction of motion produces a moving shadow? Is there a direction of motion that does NOT produce a moving shadow? Maybe you could experiment by watching the shadow your hand makes if you place it directly beneath a source of light.

    Edit: P.S. Welcome to Physics Forums.
  4. Nov 1, 2016 #3
    Thanks for that. However, i don't quite follow you ;(
  5. Nov 1, 2016 #4


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    You need to be able to attempt the question yourself. We can help you when you get stuck.

    Tom has suggested you carry out a simple experiment. It's difficult to see why you can't do that. Do you have a lamp and a table? Can you move your hand in a circle?

    Even if not, you should be able to imagine what happens using the diagram you posted.
  6. Nov 1, 2016 #5


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    Tom's suggested experiment is very easy. With a light overhead, rotate your arm in front of you so that your hand moves in a vertical circle at a constant rate. Watch the shadow. When the shadow is moving most slowly, what is yiur hand doing? What about when the shadow moves fastest?

    Edit,.. PeroK pipped me.
  7. Nov 1, 2016 #6
    Thank you. However it's really hard
    to see by naked eyes and my hands could not move at a constant rate eithe. But i think it could be B because i have thought of simple harmonic motion :|. B is equilibrium postion and V is max there , not really relevant but that's the only thing that my brain could say to me :(
  8. Nov 1, 2016 #7


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    Good reasoning. The horizontal component of motion is indeed SHM.
  9. Nov 1, 2016 #8
    Thank you so much!!
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