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Homework Help: Calculating the change of momentum in a system

  1. Oct 18, 2011 #1
    1. The problem statement, all variables and given/known data

    A ball with momentum of 10 kg-m/s [E] hits an object and rebounds with momentum of 6 kg-m/s [W]. What was the change in momentum?

    2. Relevant equations

    delta p=p(final)-p(initial)

    3. The attempt at a solution

    delta p=p(final)-p(initial)
    delta p=(6 kg-m/s)-(10 kg-m/s)
    delta p= -4 kg-m/s

    This problem seems so simple, and yet it's in the middle of a worksheet full of really hard problems, so I just wanted to make sure I'm doing it right.
  2. jcsd
  3. Oct 19, 2011 #2
    I am assuming that impact is head on i.e. there are no angles involved.

    Do not forget that momentum is a VECTOR.
    Hence if to the RHS one takes it as positive, it must be taken as negative when it reverses direction.
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