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Rotational motion & Incline Plane

  1. Feb 10, 2007 #1
    Hello everybody. I have a rather strange question regarding the rotational motion of a solid object across an incline plane. I wonder if it is possible for a solid object to move upwards the plane without the application of any external force, other than its own weight and the friction with the plane. It goes without saying that the object is not thrown across the plane. We just leave it at some point and instead of going downwards as it should this moves upwards. If anyone has any ideas on the subject i would like to hear them. Thank you.
     
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  3. Feb 10, 2007 #2

    Hootenanny

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    No, it is impossible; it would violate conservation of energy and momentum at the very least.

    P.S. Are you being serious? :surprised

    P.P.S. Welcome to the forums.
     
    Last edited: Feb 10, 2007
  4. Feb 10, 2007 #3
    It seems plausible to me. There is no conservation of momentum when you have an external friction force Hoot.

    An orbital sander will dance across the floor if you turn it on and just leave it there.
     
    Last edited: Feb 10, 2007
  5. Feb 10, 2007 #4

    Hootenanny

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    Okay, momentum was bad idea, but seriously cyrus, can you see this happening?
     
  6. Feb 10, 2007 #5
    :biggrin: How about an unbalanced wheel? If placed so, then it will roll such that it moves a short distance up the incline.

    Heck, an ordinary car can be driven up an incline with no external force other than it's own weight and the friction with the ground.
     
  7. Feb 10, 2007 #6

    Integral

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    Tape a weight to the inner side of a tin can, now place the can on the inclined plane so the weight is biased to the upper side of the inclined plane. The can will roll up the slope.
     
  8. Feb 10, 2007 #7
    Ladies and gentleman, we have a winner :biggrin:. That was a good one!

    Even when I see it, I say noooooooo that cant be right. It looks so unnatural. :rofl:
     
    Last edited: Feb 10, 2007
  9. Feb 11, 2007 #8
    That's right. It has to do with the position of the CM of the body. As far as momentum and energy conservation laws, none of them are violated since this is not an isolated system and since the CM is higher than normal we have gravitational energy converting to kinetic. Thank you.
     
  10. Feb 11, 2007 #9

    Hootenanny

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    I stand corrected :redface:
     
  11. Feb 11, 2007 #10
    It can be done. I've seen it in an ad of Chevrolet :D. If a weight is suspended inside the wheel as 'Integral' suggested and if the final state that after rolling up has a lower net energy than the wheel with weight in the first state then it would move up ti minimize its energy.
     
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