Collision of two billiard balls with spin

[jbriggs444]

So the reversal happened during the collision but not because of it? So if the other ball wasn't there, the first ball would just keep moving forward but have its rotation changed?

No. No reversal of rotation happened during the collision at all. You are trying to explain an effect that just does not happen.

Consider what happens after a collision in which a ball retains its rotational motion but reverses its linear motion.

 

[jbriggs444]

Going back and re-reading #17, the reversal of rotation is a given. We cannot argue with it. And I have been doing exactly that.

We know that the balls do not accelerate vertically so there can be no impulsive normal force. We are left with the possibility of an impulsive frictional force.

 

[FallenApple]

Going back and re-reading #17, the reversal of rotation is a given. We cannot argue with it. And I have been doing exactly that.

We know that the balls do not accelerate vertically so there can be no impulsive normal force. We are left with the possibility of an impulsive frictional force.

Thanks for confirming. Regardless, this discussion has really helped me clear up some critical misconceptions I held.

So basically, in a vacuum, when they collide, only linear velocity is reversed and each balls rotation stays the same.

On a table, it could be either way(reversal of rotation or not), depending on the type of material of the surface and material of the billiard balls. And we cannot tell ahead of time so it must be a given in the problem if we are to use frictional impulse.