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Momentum Collsion Question

  1. Sep 28, 2006 #1
    I'm not quite sure how to even start this question >-<

    But here it is: A ball with a mass of 0.75 kg initially at rest is placed at the top of curved ramp and allowed to roll down the ramp. It collides with a second ball with a mass of 0.51 kg at the bottom of the ramp which is also initially at rest. The two balls fly off the end of the ramp and land on the floor as indicated on the diagram below. Determine the range of the 0.75kg ball after it leaves the ramp if the range of the 0.51 kg ball is 4.12m. Also determine if this is and elastic or inelastic collision.


    I understand that momentum is conserved and that i have to find the time for the vertical displacement at the end, but i don't know what to do with the rest of the info i get.
  2. jcsd
  3. Sep 29, 2006 #2


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    Homework Helper

    Hint: Consider conservation of energy for the mass 0.75 kg, and recall projectile motion.
  4. Feb 24, 2008 #3
    i need help with this question as well. the hint doesnt do anything :(
  5. Feb 24, 2008 #4
    first you must find the velocity of ball 1 when it collides with the 2. Remember that if it rolls down, it has angular and linear momentum but the work of frictional force is 0(otherwise more data would be required).
    Than, you can use linear moment conservation to work out the collision part(as the range of the second ball gives you the velocity after colliding.

    hope this hint helps...xD
  6. Feb 24, 2008 #5
    if there is no friction, may i just use Vf^2 = Vi^2 + 2ad to find the velocity when it hits the ball ?

    also, to find the range, i cant seem to figure out which formula would determine that.

    i know conservation of momentum is m1v1 = m2v2

    thanks for all the help. :)
    Last edited: Feb 24, 2008
  7. Feb 24, 2008 #6
    well, use the parametric equations for the m2...is just a projectile with horizontal movement, you know the final position, the inicial position, the aceleration, you can compute inicial velocity...

    than, you got v2, m2 and m1, so you can get v1 to see if it is equal to the one you got in the energy conservation equation of m1 rolling down...
  8. Feb 24, 2008 #7
    could someone please guide me through this homework question, it just seems really complicated. if someone has time.. a step by step would be great..

    i want to learn how to do it. (not just some numbers)

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