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curator:Tim Erickson
Rolling Friction

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.

gateTime
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.
distance
is how far the cue ball traveled, measured in centimeters from the gap between the gates to the end of the cue ball (diameter: 5.5 cm).
cue_or_roll
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 comparable?

(data by Bryan Cooley, January 2003)

gateTime distance cue_or_roll
0.039 88.5 cue
0.045 66.5 roll
0.031 143 roll
0.038 95.5 roll
0.068 29.5 roll
0.04 83.5 roll
0.064 33.5 roll
0.078 22.5 roll
0.055 46 roll
0.051 51.5 roll
0.029 172 roll hit sticker
0.03 168.5 roll
0.032 128 roll
0.049 58 roll
0.031 136 roll
0.044 71 roll
0.036 110 roll
0.064 34.5 roll
0.036 105 roll
0.039 90 roll
0.026 196.5 roll
0.027 174 roll
0.05 55.5 roll
0.026 183.5 roll

<text form of the data>

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Last updated 23 January 2003
supported by NSF award DMI-0216656