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The significant deformation of both the tip and the end of the shaft during the contact phase makes me suspect that the rotation induced deflection force is not the only force here acting downward from the line of the cue's initial movement.
What's the "rotationally induced deflection force"?
Colin Colenso said:
I still don't know how to explain this in physics terms though, other than with the speculation of the significant influence of millions of micro-slip collision being involved. I did a little reading of the effects of the stick-slip friction phenomenon which is common in moving static like collisions. Such as the brake pads on the wheel rims, or the dragging of a block across a surface with an elastic spring.
Sure, engineers talk a lot about slip-stick friction. We've all experienced it. But there's no reason to propose something like that for the tip-ball collision, is there? Am I missing something?
Colin Colenso said:
I suspect the static model concept works well as an approximation for most tip-CB collisions, but at the nano-level it certainly can't be entirely true.
I agree the static model works well for most --nearly all-- tip-ball collisions. It doesn't work at all for a miscue. And I suppose that right at the miscue limit, things are more complicated. Suppose, for instance there is a small area of chalk at the part of the tip that first contacts the cueball. The collision will start as normal (static), but when the tip compresses further, the collision might turn into a miscue.
The nano stuff is a red herring. Ours is a bona fide, tried & true MACROSCOPIC system. Sure, friction is hard to understand and hard to model at the nano level. For mems technology, that's important. But for us, it's not important, not even a little. I have friends who use molecular dynamics simulations to try to model friction at the nano level. These guys know that as their system gets big, their model should converge to macroscopic phenomenological observations like Amonton's law. They worry about it if it doesn't.
Colin Colenso said:
At higher speeds some other things are going on that have significant effects.
At higher speeds? I don't know what you mean.
Colin Colenso said:
btw: Another piece of possible evidence for the pie is that stiffer shafts tend to squirt less (in my experience). Something that would tend to contradict the rotation induced deflection model but add weight to the idea that a cue deforming to increase overall offset is playing a role here.
Hope some of that waffle makes sense
Colin
I don't agree that stiffer shafts squirt less. I don't know what the rotation induced deflection model is, but I don't thnk a stiffer shaft deforms less while in contact with the ball. It just bends to a lower amplitude after the ball is gone. A soft tip, on te other hand, will lead to a greater effective offset because it is on the rotating ball longer. Presumably the squirt and the spin on the ball will match the effective offset.
mike page
fargo
