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Friction or some force acting on momentum of an object

  1. Oct 28, 2006 #1
    Would forces like friction and air resistance increase momentum or decrease it?

    I would think if a force acts on momentum it would decrease the momentum of an object. Is that right?

    P= mv

    P= Ft
  2. jcsd
  3. Oct 28, 2006 #2


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    It depends on the direction of the force with respect to velocity. In the case of friction and air resistance, the absolute value of the momentum will always decrease, yes.

    It should be noted that if the momentum is negative, it will actually increase
  4. Oct 28, 2006 #3
    Of course it would decrease it, but this is assuming a certain refrence frame.
    If for some reason the refrence frame were moving, then friction could increase momentum.
  5. Oct 28, 2006 #4
    or I guess it could decrease it and then start increasing it.

    <<just to confuse you :) >>
  6. Oct 29, 2006 #5
    I am sure you are familiar with friction decreasing momentum. An example of friction inceasing momentum would be the way a car accelerates. The force that pushes the car forward is actually friction from the road on the tyre. The car accelerates and increases its momentum.
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