I had a small doubt in pool physics..

I just googled, the average speed when a cue strongly strikes a ball.. its about 10m/s.
And cue ball is about 3cm in radius.
That gives a typical angular speed of over 50 rotations per second!.. and that doesn't seem right :-/
what am I missing?

Question

I had a small doubt in pool physics..

I just googled, the average speed when a cue strongly strikes a ball.. its about 10m/s. 
And cue ball is about 3cm in radius.
That gives a typical angular speed of over 50 rotations per second!.. and that doesn't seem right :-/
what am I missing?

anonymous · Answer

@ganeshie8 @Vincent-Lyon.Fr @Kainui

anonymous · Answer

depending on where exactly do you hit the ball (near the edge or dead center). I googled the weight for a cue ball and got something like 0.17kg and it's diameter is roughly 2-3 inches

Assuming sphere is solid I'll say the number makes sense

vincent-lyon.fr · Answer

I am no expert, but I think the cue will slip on the ball, and you cannot equate w=v/r

vincent-lyon.fr · Answer

This page is interesting, but I could find no mention of cue-ball interaction. http://www.real-world-physics-problems.com/physics-of-billiards.html

anonymous · Answer

@Vincent-Lyon.Fr 
Its always possible to strike it so that it immediately enters into pure rolling right?
If it is hit at 7/5 R from the bottom!

@alias
Thanks for the verification.

anonymous · Answer

@Mashy
Have you played much pool?

anonymous · Answer

A cue ball has a circumference of abut 9 cm. so a 50 rpm assuming so slipping that gives a translational speed of about 4.7 m/sec. which  is not unreasonable. But the physics is difficult because of the slippage of the cue on the ball and the friction of the ball with the table.

vincent-lyon.fr · Answer

Quote: Its always possible to strike it so that it immediately enters into pure rolling right? If it is hit at 7/5 R from the bottom!

You are right, but in my post, I did not mean slipping between the ball and the table, but between the ball and the cue stick. If such slipping happens, you cannot transfer angular momentum as efficiently as thought initially.

anonymous · Answer

@gleem No I haven't played at all :D
@Vincent-Lyon.Fr 
Yea well.. but my main question was, the order of magnitude of the rotation speed of the cue ball.. It just seemed to me that about 30 or 40 rotations per second was way to high

Also @gleem I like to to point out its rotations per SECOND. not minute. 

so these rotations are reasonable and not ridiculously high right? :D

anonymous · Answer

@Mashy
 Oops that rpm was a typo and I forgot a factor of 2 so the linear speed is 9.4 m/s for 50 rps.  actually not all that fast about 34 Kph.

anonymous · Answer

thanks a lot :)