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Homework Help: Pendulums colliding - collision

  1. Nov 14, 2006 #1
    In the figure View Figure the upper ball is released from rest, collides with and the stationary lower ball, and sticks to it. The strings are both 50.0 cm long. The upper ball has mass is 2.00 kg and it is initially 10.0 cm higher than the lower ball, which has mass 3.00 kg.


    Find the maximum angular displacement of the motion after the collision.

    I've found omega, if that helps.
  2. jcsd
  3. Nov 14, 2006 #2


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    since we don't know what omega is, it doesn't.

    Convert the potential energy the ball being held up starts with into the kinetic energy it will have when it strikes the bottom ball. Then use conservation of momentum for an inelastic collision, and convert the new kinetic energy to the maximum potential energy the system can achieve. From there, use trig
  4. Nov 14, 2006 #3


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    Use conservation of energy to find the speed of the first mass just before it hits the second one. Then use momentum conservation to find the speed of the two masses combined just after the collision (when they are still at the lowest point). Finally, use conservation of energy again to find how high they will swing up. Once you have that, simple geometry will give you the angle they reach.
  5. Nov 14, 2006 #4
    can you give me a hint with the trig? Because I can only find one side, and the right angle. I need at least one more angle or side.
  6. Nov 14, 2006 #5
    nevermind, I got it. Thanks for the help.
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