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Homework Help: Momentum, what velocity do i use?

  1. Mar 27, 2010 #1
    1. The problem statement, all variables and given/known data
    I have done a cart experiment, were 1 cart collides with another that is stationary in a straight line. i have videotaped my experiment and used logger pro to evaluate my findings. it gives me different velocity's, in each time frame. which velocity do i use to work out the momentum?

    2. Relevant equations

    3. The attempt at a solution
    i used the equation d=1/2(u+v)t
  2. jcsd
  3. Mar 27, 2010 #2
    You simply use the velocity at the point of incident ie at the collision point. Normally in physics you might be expected to deduce the velocity from a function that describes the movement of the rolling cart. You don't need to do this because you have the raw data. Bonus points, though for describing the deceleration of the trolley with an appropriate function and then comparing function with your results. Good luck
  4. Mar 27, 2010 #3
    thank you
  5. Mar 28, 2010 #4
    which velocity do i use to work out how much momentum the cart getting hit has if its starts staionary
  6. Mar 28, 2010 #5
    Momentum is what an object possesses only when it is moving. The equation p=mv states that momentum (p) is equal to mass (m) times velocity (v). Momentum is used as a means to define an object by it's mass and speed. Since your cart was hit whilst stationary it's speed was zero therefore it's momentum was zero.
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