Speed and Spin - the physics

[Pin]

Putting spin, and most notably draw, on a cue ball.
A lot of people consider cue acceleration to be crucial, as opposed to cue speed.

I know in determining cue ball speed, cue speed is the decisive factor, by conservation of momentum (where momentum = mass x speed).

But is it momentum that determines spin, or is it force? (where force = mass x ACCELERATION).

To me, it seems like it should be force. That'd best fit my recollection of high school maths. But that's hardly conclusive.

From experience, again, acceleration seems most important. It'd explain why my draw is so inconsistant at similar speeds.
Though here acceleration could just be relevant in that it forces you to shoot 'through' the CB, giving a better contact and thus more spin. If so, it's not really a magic formula for adding draw.


Anyone able to shed some more light on the subject? Mathematical knowledge would be good, but I'd accept observations and experience

 

[Ken in CT]

Mass x acceleration refers to the effect on the cueball and not on what the cue is doing. The mass of the cueball times the acceleration it undergoes is a measure of the force it experienced. That force came from the momentary contact of the cue and its momentum plus any push you might be exerting with your stroke.

Whether the cue is accelerating or not might alter the average speed the cueball feels during the brief time the cue is in contact with it. That time is so brief that cue acceleration would be very small and insignificant. It may well be a more effective method of producing draw, however. Pushing through the shot by trying to accelerate the cue may be a better way of performing a draw stroke but not because the cueball has any idea that the cue is accelerating. It might increase the contact time between the tip and the ball.

Nevertheless, don't think of the force equation as having any relationship to the acceleration of the cue. It is the cueball that accelerates due to the pushing force of the cue. The nature of that pushing has nothing to do with that force equation.

If course, you can back up one step and say that the force your stroke imparted to the cue can be measured by the mass of the cue times its acceleration but the cueball doesn't care how the cue got moving.
Ken

 

[Billy Jungle]

pool and physics

I would refer any and all cuestions in the matters of pool/physics to Bob Jewett no one is more knowledgable than he IMHO.

 

[Pin]

Thanks.
Ken's explaination seems to make sense. I guess I just need to look a little harder for whatever it is that gives me huge spin sometimes and virtually nothing others...