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Re: Rolling, Static, and Kinetic Friction



Leigh Palmer wrote:
...
It is said: "A difference, to be a difference, must make a difference."
Since the dynamical effect is the same for rolling, static, and sliding
friction, why distinguish among them at all for the high school student?

Since when is the dynamical effect the same? Static friction is a force
of constraint that prevents relative motion parallel to two contacting
surfaces and which dissipates no energy. Various kinetic frictions (i.e.
rolling, sliding, etc.) provide no constraint and *do* dissipate energy. This
is a *significant* difference--even for high school students.

David Bowman
dbowman@gtc.georgetown.ky.us