# Q & A: rolling friction

Most recent answer: 06/05/2011
Q:
Question 2)Suppose you are a billiard player. You throw your ball with a speed of v=5m/s on another ball at a distance d=1m. Your billiard table has a friction with a coefficient of mu=0.5. the two ball collides head on and 10% of energy is lost during collision. How far the second ball can go on this table? The mass of billiard ball is m=220g.
- mrv (age 20)
turkey
A:
This problem is puzzling. Once the ball is rolling, the standard coefficient of friction gives no information about how much it will slow down. That's because the nominal point of contact isn't sliding on the table.  In practice, there is some frictional loss of energy to heat even in rolling friction, but it's small and not given by the usual coefficient. So if we were to treat this as a textbook problem, just using the information given, we'd say the ball would roll infinitely far. (Of course the table may not be quite that big.)

Mike W.

(published on 06/05/2011)