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Friction on an inclined plane

  1. Jul 29, 2012 #1
    If we Are moving an object on an inclined surface than shouldn't friction be in the same direction?
     
  2. jcsd
  3. Jul 29, 2012 #2

    Doc Al

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    Same direction as what? The motion of the object?
     
  4. Jul 29, 2012 #3
    Friction is always in the opposite direction to the direction of movement of an object.
     
  5. Jul 29, 2012 #4

    arildno

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    Not exactly.
    It opposes the RELATIVE motion the object has to say, the underlying surface.

    That is:
    Friction seeks to equalize the motions of the object and the surface.

    Suppose you drop a brick (no horizontal velocity) onto a moving plank.
    The friction from the plank will accelerate the brick in the direction of its own generated horizontal motion, until the brick moves with the same speed as the plank.
     
  6. Jul 29, 2012 #5
    So friction will oppose the motion
     
  7. Jul 30, 2012 #6

    arildno

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    It opposes relative motion between the object and the surface.
     
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