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Re: Rolling, Static, and Kinetic Friction



Hi all-
Leigh Palmer writes:
*************************************************************
I concede your point, but my plea was for dynamical effects. Static
friction can certainly change the kinetic energy of a car just as
surely as can sliding friction or rolling friction. That the latter
two dissipate energy* while the first changes it conservatively
is of secondary importance in an introductory course. Once the
students know what F = ma means, and believe it, Then one can go on
to more sophisticated topics.
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I disagree. Consider the following problem, which I always
include on friction quizzes and tests:
A 75 Kg skier stands on horizontal, snowy surface. Coef of
friction between skis and snow is .02. The skiers friend pushes her
forward with a steady force of 1 N. Calculate the acceleration of
the skier.
About 80% of all students have the skier accelerating
backwards.
Regards,
Jack