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Homework Help: Rolls down a ramp and bounces back up

  1. Nov 13, 2005 #1
    Hi guys (and girls), I'm kinda new to these forums. What I mean by that is I haven't yet posted anything, but I have been lurking around for a few weeks. Anyways, I'm stuck on this homework problem.


    A 500 g cart is released from rest 1.0 m from the bottom of a frictionless, 30 degree ramp. The cart rolls down the ramp and bounces off a rubber block at the bottom. The figure shows the force during the collision.

    knight_Figure_09_30.jpg


    I have setup my force diagram and found the following information:

    Fnet(x): 2.45N
    Velocity at bottom of ramp: 3.13m/s
    Time to reach bottom of ramp: 0.64s



    Unfortunately, I don't know what to do next.

    This problem is very elementary I know, but all help will be appreciated.
     
    Last edited: Nov 13, 2005
  2. jcsd
  3. Nov 14, 2005 #2

    SpaceTiger

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    So...what is it asking you to do?
     
  4. Nov 14, 2005 #3
    Sorry guys. I forgot to ask the question...haha. But anyways, I figured it out. I forgot an important part of the conservation of momentum theorem.

    Just for the record, the question was "How far up the ramp does the cart rebound?"
     
  5. Oct 26, 2006 #4
    Hey guys, I have the same problem and I just happened to find this thread

    I took J which is the area under the force curve in the diagram so I have 26.7N

    Then P2x = p1x + Jx = (3.13m/s * 0.500kg) + 26.7N = 28.265 kgm/s

    Then V2x = 28.265kgm/s / 0.500kg = 56.53m/s? I think I might have screwed up because I dont think it can have that velocity.

    Now I don't know where to go once I have the velocity

    nevermind I didnt convert ms to s correctly, now I have a post collision velocity of 8.47m/s but I don't know what to do after
     
    Last edited: Oct 26, 2006
  6. Oct 26, 2006 #5
    Hi,

    I have the same question but where's the 3.13m/s coming from?
    Here I try to do it the fancy way.
    I did
    [tex]\[ v^2_f = v^2_i + 2ad \]
    \[ v^2_f = 0+ 2(mgsinx)(1)\]

    so /[v_f = 2.21 m/s \] [/tex]

    I took area like the last guy expcept I got 2.67Ns

    Then I did whole bunch of other stuff to get wrong answer so can somebody help me with the first part?
     
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