Rolling friction is generally small. How can we
measure it? Does it work the same as other friction?
We tried the following: we rolled a cue ball through a pair of
Vernier photogates, and then measured the distance from the gates
to where the ball stopped.
- is the time in seconds between the time the ball interrupted
the beam on the first gate and the time it interrupted the beam
on the second. The distance between the beams is 15 mm.
- is how far the cue ball traveled, measured in centimeters from
the gap between the gates to the end of the cue ball (diameter:
- describes how the ball was sent, and any unusual occurrences
What is the relationship between gateTime and
the speed of the ball?
Are the data consistent with uniform deceleration? (They are, more
or less. How do you show that?)
What could explain any inconsistencies?
What is a reasonable value for the coefficient of rolling friction
in this setup? Do you need the mass of the cue ball?
Find references to this quantity on the web. Is your coefficient
(data by Bryan Cooley, January 2003)