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Homework Help: Billiard Balls problem

  1. Sep 15, 2008 #1
    Two billiard balls are moving on a (coordinatized) pool table according to the respective paths x(t)=(t2-2, [tex]\frac{t^2}{2}[/tex]-1) and y(t)=(t, 5-t2)
    where t is time in seconds.

    a) When and where do the balls collide?
    I found where the 2 graphs intersect to be (2,1) so does that mean at 2 seconds 1 unit of distance away?

    b) What is the angle formed by the paths of the balls at the collision point?
    This is where I am stuck. Any hints on how to figure this out?

    This is due Thursday and any help would be appreciated. Thanks!
  2. jcsd
  3. Sep 15, 2008 #2


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    Science Advisor
    Homework Helper

    Yes, they intersect at t=2. Good so far. The last question you asked showed you know how to find tangent vectors to a curve. If you find the two tangent vectors do you know how to find the angle between them (think 'dot product')?
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