How long are the CB and OB in contact during a collision?
Marlow did some experiments on this, and he reported numbers between 0.0001 and 0.0006 seconds (in “The Physics of Pocket Billiards,” 1995). The balls do not stay in contact for very long.
Alexander Sorokin has also taken various measurements of ball properties and contact times. More info can be found here: Collision of Billiard Balls. They measured ball contact times in the 250-300 micro-second range (0.00025-0.0003 seconds).
Here’s a super-slow-motion view showing how brief the balls remain in contact (and how little they compress):
See also: ball compression effects.
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