What is the speed of the 8-ball after the collision?

  • #1

  1. In a pool game, the cue ball, which has an initial speed of 1.3 m/s, makes an elastic collision with the 8-ball, which is initially at rest. After the collision, the 8-ball moves at an angle theta = 33.2o with respect to the original direction of the cue ball, as shown in the figure. Assume the pool table is frictionless and the masses of the cue ball and the 8-ball are equal. What is the speed of the 8-ball after the collision?

    prob11a.gif





2. Mgh + W = 1/2mv^2
p=mv



3. I was easily able to get that phi was 56.8 deg because of the 90 deg angle. Now I am lost at how to find the velocity of the 8 ball without the velocity of the cue ball???
 

Answers and Replies

  • #2
BvU
Science Advisor
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Hello White and welcome to PF :-)

Your collection of relevant equations needs revision and extension. Mgh and W are unlikely to play a role in this drama....
 
  • #3
HallsofIvy
Science Advisor
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Conservation of momentum and energy are most important. But "Mgh" is irrelevant here. It is the potential energy of a mass M at height h, but there is no "height" here.
 

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