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Homework Help: Conservation of Momentum initial velocity curved path

  1. Apr 7, 2009 #1
    1. The problem statement, all variables and given/known data
    The frictionless track is made of a straight horizontal section and a quarter-circle with radius R = 5 m. A 1 Kg lump of putty is thrown toward the stationary 4 Kg block, and the block starts to slide with the putty stuck on it after the collision. If the normal force acting on the block/putty from the track is 98 N at point B, find the initial speed v0 of the putty.

    2. Relevant equations
    ....energy equation?

    3. The attempt at a solution
    I have been trying to use the energy equation to solve this problem but I am getting nowhere. The answer is 70 m/s. I can't seem to figure out what the velocity would be at the bottom of the arc. According to a(norm)=v^2/R, I found that v=9.8995 but don't know what to do with that...

    Attached Files:

  2. jcsd
  3. Apr 7, 2009 #2


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    Homework Helper

    Well depending on where B is the velocity would be different.

    But say B is just at the bottom of the arc, then on the arc the forces acting are the Normal force R and the weight W. The resultant of these two gives mv^2/r


    so find v from that.

    Then put that into the momentum equation.
  4. Apr 7, 2009 #3
    Ok I got it now. Thanks for the help.
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