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Homework Help: A momentum analysis lab trying to get a better understanding

  1. Nov 9, 2009 #1
    1. Dropped a .057kg tennis ball and .0027 kg pingpong ball (the pingpong ball is resting directing on top of the tennis ball) from .5 m. Measure the height of the pingpong ball's rebound.

    PPm = .0027 kg
    TBm = .057 kg

    PPwidth = .04 m
    TBwidth .065 m

    Drop Height:

    PP = .565 m
    TB = .5 m

    Post Collision Height:

    PP = 1.3 m
    TB = approx. .12 m*

    * We observed the height of the to be approx. .12 m., but this is where my confusion starts. I am not sure if the collision occurred at .12 m because the balls drop at different speeds.(and the TB hits the ground first, then collides with the PP at .12 m) OR if the balls drop together and hit the ground as one unit, with the PP taking most of the KE upward to the 1.3 m, and the TB only rebounding .12 m after transferring its energy.

    2. V2 = Vo2 + 2a(d)

    3. So how would you look at this experiment and where would you note the transfers of energy.

    At this point I am looking at as the TB dropping at a certain velocity, with the PP directly above it falling at another velocity. (During the fall a small displacement occurs between the two balls) The TB collides with the earth, and rebounds in the opposite direction with essentially the same momentum. (The transfer of energy between the TB and earth is infinitesimally small) The falling PP collides with the TB at the .12 m. This is a second collision. The one that I want to analyze.

    So with P = mv and KE = 1/2mv^2, and the assumption that P1 = P2, we have the (Ptb1 + Ppp1) = (Ptb2 + Ppp2) I can figure the momentum of all the objects, but I am still not sure how to view the problem.

    I am looking for some ideas of how one would attack this problem. I completed the experiment and handed in my report, but I am trying to gain a better understanding of how to view the event. (my physic's vision (as my prof calls it) is not developing as quickly as I would hope)
  2. jcsd
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