Mark Wilson's "additional friction" comment

I think what you said may be very accurate for most common ball-ball collisions on pool tables, but in general they can be quite different, e.g. kinetic vs. static frictions between ball and cloth, between cuetip and ball.

Only at very high speeds. For most shots seen on a pool table, kinetic and static friction are nearly the same.

Freddie
 
Only at very high speeds. For most shots seen on a pool table, kinetic and static friction are nearly the same.
The physics of throw is not a simple matter of kinetic vs. static friction. With a frozen CB or a frozen-OB combination, one might think "static" friction applies. However, there is still sliding between the balls during contact. If the cut angle between the balls is on the small side (less than about 20 degrees), sliding stops during contact and the balls "gear" together. In this case, the amount of throw doesn't vary at all with shot speed. For larger cut angles (greater than about 20 degrees), where sliding occurs during the entire contact period, the amount of throw is less at faster speeds because the effective "kinetic" friction is less at faster relative surface speeds.

FYI, items 16-27 in the numbered list on the squirt/swerve/throw effects resource page summarize all throw effects (with supporting articles and demonstrations). If you look at this list, it is clear that throw is not a simple matter of "static" vs. "kinetic" friction.

For those interested in the math and physics details, they are presented in TP A.14 - The effects of cut angle, speed, and spin on object ball throw. The articles linked from the squirt/swerve/throw effects resource page attempt to present and illustrate the results of the analysis and supporting experiments in simple terms with examples.

Check it out,
Dave
 
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