Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Linear momentum handball problem

  1. Oct 9, 2008 #1
    1. The problem statement, all variables and given/known data
    A handball of mass 0.10 kg, traveling horizontally at 30 m/s, strikes a wall and rebounds at 24 m/s. What is the change in the momentum of the ball?


    2. Relevant equations

    change in momentum = mv2 - mv1

    3. The attempt at a solution
    Do you take 24 as negative or positive? If you take it as neative you get -2.4-3=-5.4 if you take it as positive you get 2.4-3= -.60
    both answers given in the problem are either positive 5.4 or positive 6.0. Thanks for your help
     
  2. jcsd
  3. Oct 9, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    If you take the 30 m/s velocity as positive, then you'd better take the 24 m/s as negative since it's going in the opposite direction. For the final answer they just want the magnitude of the change in momentum, which is always positive.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook