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Rubber ball colliding with steel ball of equal mass

  1. Feb 16, 2014 #1
    1. The problem statement, all variables and given/known data
    Suppose a rubber ball collides head-on with a steel ball of equal mass traveling in the opposite direction with equal speed. Which ball, if either, receives the larger impulse? Explain.


    2. Relevant equations
    p = m*v
    impulse force = change in p

    3. The attempt at a solution

    (1) At first I intuitively thought that since the rubber ball is more "bouncy" than the steel ball, it'll likely bounce off after the collision and travel in the opposite direction at a greater speed than the steel ball will. So I thought that the rubber ball will have larger change in momentum, and thus will exert more impulse, meaning the steel ball will receive the larger impulse.

    (2) But then, I began thinking that my intuition may not be correct. The momentum change must be the same for both balls regardless of whether they're steel or rubber, meaning the impulse force must be equal....also, impulse is nothing more than the integral of the force exerted during some time interval. The balls collide for the exact same time interval, and the force exerted by the balls on each other is also the same.

    Is answer (2) correct? If so, would the answer remain the same if the question were changed to the following: "Suppose a rubber ball collides head-on with a steel ball of equal mass traveling in the opposite direction with **DIFFERENT** speeds."

    Thanks a lot.
     
  2. jcsd
  3. Feb 16, 2014 #2

    SammyS

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    The second version is a very good analysis, especially the use of Newton's 3rd Law.


    For the second scenario, ... how would your previous answer have to be modified? -- if at all ?
     
  4. Feb 16, 2014 #3
    Thank you for your response SammyS. My guess is that the answer should not change for the second scenario (where the balls' initial speeds are different), since the force exerted by the balls on each other should be the same in magnitude regardless of whether their initial speeds are the same or different...and the time interval of the force should also remain the same...is this reasoning correct or am I off base?
     
  5. Feb 16, 2014 #4

    SammyS

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    You are correct with that answer !
     
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