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Movement of a plank

  1. Jul 10, 2013 #1

    adjacent

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    Here is a plank in empty space(There are no forces except one) .Someone is pushing it on a side.Will it rotate or Move straight in the direction of the force?
     

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    adjacent, Jul 10, 2013
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  3. Jul 10, 2013 #2

    Doc Al

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    What do you think? Apply Newton's 2nd law for translation and for rotation.
     
    Doc Al, Jul 10, 2013
  4. Jul 10, 2013 #3

    adjacent

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    I don't quite understand that.:confused:
     
    adjacent, Jul 10, 2013
  5. Jul 10, 2013 #4

    WannabeNewton

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    Write down ##F = ma## and ##\tau = I\alpha## for the system you drew.
     
    WannabeNewton, Jul 10, 2013
  6. Jul 10, 2013 #5

    adjacent

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    OMG!What's ##\tau = I\alpha## ?
     
    adjacent, Jul 10, 2013
  7. Jul 10, 2013 #6

    Nugatory

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    Something that doesn't easily hit in google :)
    Try googling for "moment of inertia" and "torque"
     
    Nugatory, Jul 10, 2013
  8. Jul 10, 2013 #7

    Doc Al

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    Doc Al, Jul 10, 2013
  9. Jul 10, 2013 #8

    adjacent

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    I have not heard about anything about the moment of inertia or angular acceleration.Anyways,The plank will rotate,Am I right?
     
    adjacent, Jul 10, 2013
  10. Jul 10, 2013 #9

    Doc Al

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    The motion of the plank will be a combination of the translation of the center of mass plus rotation about the center of mass. It will rotate as well as translate.
     
    Doc Al, Jul 10, 2013
  11. Jul 10, 2013 #10

    adjacent

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    Then where should I apply a force so the plank will only move straight without rotating?On the center of Mass?
     
    adjacent, Jul 10, 2013
  12. Jul 10, 2013 #11

    Doc Al

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    Yes, at the center of mass.
     
    Doc Al, Jul 10, 2013
  13. Jul 11, 2013 #12

    adjacent

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    When I apply the force on the sides it will rotate and translate,What will happen if I remove the force.Will the plank keep rotating and translating or Move in a constant velocity in a straight line?
     
    adjacent, Jul 11, 2013
  14. Jul 11, 2013 #13

    Doc Al

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    When you remove the force, the center of mass will continue moving in a straight line at constant speed. And the plank will continue to rotate about its center of mass with a constant angular velocity.
     
    Doc Al, Jul 11, 2013
  15. Jul 11, 2013 #14

    adjacent

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    Thank you So much Doc Al
     
    adjacent, Jul 11, 2013
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