We are grateful for the feedback we've received from Gabriel Kessler regarding our example of using dimensionless plots. Kessler captures the spirit of this technique with his suggestions for a modified analysis with the parameter F/(m2g)⁠. We also agree that the analysis should yield a coefficient of kinetic friction that is less than the coefficient of static friction for the maximum force of static friction. However, what we attributed to experimental error associated with numerical differentiation was more likely an oversight in the analysis. Private communication with Donald Fahnline helped us identify this mistake.

Topics
Friction, Numerical differentiation
1.
Daniel
Ludwigsen
 and
Kathryn
Svinarich
, “
Choose wisely: Static or kinetic friction—The power of dimensionless plots
,”
Phys. Teach.
47
,
158
–
161
(March
2009
).
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© 2009 American Association of Physics Teachers.
2009
American Association of Physics Teachers
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