Momentum in Billiards
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Here's a question... how can one pool ball knock six others into the pocket? The answer: conservation of momentum. I like to think of the stagnant six pool balls as one single object. If the cue has mass 'M,' the object including the corner balls has mass 6M. Using conservation of momentum... [ATTACH]50[/ATTACH]
and that after this (nearly) elastic collision, the velocity of the cue ball is 0...
MV + 6M(0) = M(0) + 6MV'
Therefore, V', or the velocity of the six balls, is V/6.
The smaller velocity of each of the six balls explains why one ball can move six. While each ball after the collision is moving slower, the sum of all of their momenta equals that of the cue ball before the collision.
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