# I Bounce of the cue ball in snooker

#### TSN79

I was watching a game of snooker, and sometimes the cue ball bounces off the cushions with surprisingly high speed. Some people often say that it comes off the cushion faster than it went into it. And I started thinking - is that even possible? Does physics work that way?

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#### tkyoung75

Maybe if it has spin

#### pinball1970

Gold Member
Maybe if it has spin
Yes top spin giving angular momentum which will not be apparent from a normal view point. You can see a slowed down cue ball with spots more easily like in this video.

#### A.T.

is that even possible? Does physics work that way?
Have you ever played with a "superball" (high friction bouncy rubber ball)? If you give them lots of spin, they shoot off very fast at bounce. Rotational kinetic energy is converted into linear kinetic energy.

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#### PeroK

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I was watching a game of snooker, and sometimes the cue ball bounces off the cushions with surprisingly high speed. Some people often say that it comes off the cushion faster than it went into it. And I started thinking - is that even possible? Does physics work that way?
I think the effect is that the trained eye expects a certain reduction in speed upon impact with the cushion. When this doesn't happen and the ball rebounds faster than expected it creates the illusion that it speeded up.

That said, I would like to see some analysis of the speed of a ball before and after it strikes the cushion.

The cases in question are not where spin is involved. Those cases are known and understood.

#### pinball1970

Gold Member
I think the effect is that the trained eye expects a certain reduction in speed upon impact with the cushion. When this doesn't happen and the ball rebounds faster than expected it creates the illusion that it speeded up.

That said, I would like to see some analysis of the speed of a ball before and after it strikes the cushion.

The cases in question are not where spin is involved. Those cases are known and understood.
Will the spin not be transferred to the cushion once it strikes?

Intuitively I would thought the energy is transferred to a small point on the rubber cushion which recoils then springs back pushing the cue ball out again.

This is from playing the game (pool not snooker) and trying to adopt some physics I understand (to some extent)

Also, I found this study from Loughborough university – it made sense then got tricky edit not impossible

https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/15087/3/Ball%20behaviour%20under%20under%20cushion%20impacts.pdf

Let me know what you think and an idiots guide would be appreciated.

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#### tkyoung75

I could not find a standard coefficient of restitution for billiard cushions, although the above reference indicates what one might expect. The cushions are made of rubber (natural or synthetic), and accuracy of bounce over a range of speeds is a key performance measure.

"Bounce of the cue ball in snooker"

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