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Homework Help: Calculating Momentum

  1. Feb 24, 2006 #1
    Can anyone help with this ???
    A 220g ball falls vertically downward, hitting the floor with a speed of 2.4 m/s and rebounding upward with a speed of 1.8 m/s.
    A.) Find the magnitude of the change of the balls momentum (up=positive)
    i used p=mv; (.22kg)(1.8) = .396 as well as (220g)(1.8)=396

    B.) Find the change in the magnitude of the balls momentum. (Neg. value=decrease in magnitude)

    Can anyone help on this 2 parts?
  2. jcsd
  3. Feb 24, 2006 #2
    i guess its right the way you have done it....
  4. Feb 24, 2006 #3
    I'm not sure what the difference between a and b is supposed to be...

    Anyway, [tex] \mathbf{\Delta p} = \mathbf{p_f} - \mathbf{p_i}[/tex]. Remember that these are vectors, so in your coordinate system, the initial p is negative, your final p is positive.

    Watch the units! Your first calculation is good, but your second is wrong since you are using g, not kg.

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