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Homework Help: Collisions in 2 dimensions

  1. Dec 7, 2005 #1
    having trouble with this problem in my text book

    two pucks collide, puck A has a mass of 0.32kg, and an initial velocity of 0.04 m/s [54 N of E], and a final velocity of 0.034 m/s [N]
    puck B's mass is unknown but has an initial velocity of 0.038 m/s [S of W] and a final velocity of 0.028 m/s [46.5 N of E]. Puck B's mass needs to be found.

    Wheni tried it i used components but i did not get the right answer, the answer in the back of the book is 0.22kg. Does anyone else get this answer? if so could you explain how?? thanx.
  2. jcsd
  3. Dec 7, 2005 #2
    what equations did you use....i'm assuming pure elastic?
  4. Dec 7, 2005 #3
    yeah i assumed that it was pure elastic, the equation used was..

    (m1x)(v1x) +(m2x)(v2x) = (m1x)(v1fx) +(m2x)(v2fx)

    (m1y)(v1y) +(m2y)(v2y) = (m1y)(v1fy) +(m2y)(v2fy)
  5. Dec 7, 2005 #4


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    Could you show me your complete procedure?
  6. Dec 7, 2005 #5
    try using the conservation of Energy rather than momentum....cuz with teh Cons of Mom...it'd be best if you showed those angles...sorry lazy to draw it out myself.
  7. Dec 8, 2005 #6
    bah! sorry for wasting your time, i measured the one angle wrong it was 45 instead of 54!! thanx for your time though, with that change the problem does work out to the solution in the back.
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