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Oblique Impact of a smooth sphere against a fixed plane

  1. Jun 10, 2013 #1
    A sphere of mass 'm' collides with a fixed plane with initial speed 'u' at an angle 'α'(alpha). The sphere rebounds with speed 'v' at an angle 'β' with the normal. The plane being fixed remains at rest.
    We applied Newton's Experimental law( along the common normal(CN)
    The equation after applying Newton's Experimental law along CN becomes:
    Vseperation along CN =eVapproach
    where 'e' is the coefficient of restitution.
    On the other hand, we applied Conservation of Momentum along the Common Tangent(CT) as there is no force along CT.
    So after applying conservation of momentum along CT we get the following equation:
    But we could have also conserved momentum along CN as there is no net force acting along the CN. This is because during collision,
    N(Normal Reaction)=mg(weight of the sphere)
    But since this is not done so it means that there is a net force along CN. What is that force? Or rather, what is that NET force? I think it is Impulse but why does the Impulsive force become greater than the weight of the object at the time of collision? Also, how does that impulsive force arise? Is it because of the normal reactions that the ball and the floor impart on each other when the ball collides with the floor or and Impulsive force is a completely different force just like Normal Reaction? Since the ball bounces back there has to be a net vertical force in the upward direction at the time of colliding. That is impulse..but why? Also, why is it specifically mentioned that the sphere is smooth? What would happen if it won't be smooth?Please reply fast!
  2. jcsd
  3. Jun 10, 2013 #2
    Please reply soon! :)
  4. Jun 11, 2013 #3


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