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Help on 2 problems

  1. Nov 13, 2005 #1
    Hey all, I am in need of desperate help, any comments would be a huge help! thanks.

    A proton moving at 3x10^5 m/s [E], strikes a helium nucleus at rest. If the collision is perfectly elastic, find the velocities of each after the collision. Assume the collision is 1 dimensional.

    A tennis ball of mass m and speed v strikes a wall at 45degree angle and rebounds with the same speed at 45degrees. What is the impulse given the wall? [Hint: Magnitude and Direction are needed]

    Thanks for any help,
  2. jcsd
  3. Nov 13, 2005 #2


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    Staff Emeritus
    Science Advisor

    For 1, try conservation of momentum and conservation of energy.

    So mHvH is the momentum before, and must equal the momentum after, and

    1/2 mHv2H is the KE before and must equal the KE of both particles after.

    Use the relationship of momentum to partition the KE. The problem stated represents a head-on collision with full recoil.

    For 2, the change in momentum normal to the plane of the wall contributes to the impulse. The momentum parallel to the wall does not contribute to the impulse.
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