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Date: Wed, 11 Mar 1998 19:20:37 -0500
Reply-to: phys-l@mailer.uwf.edu
From: Jerome Epstein <jerepst@worldnet.att.net>
To: phys-l@atlantis.uwf.edu
Subject: Re: Favorite Test Questions
There is a lot of good physics here. If nothing else, thisLike most of your students, I am also having difficulty
answering the above question. According to my dictionary
and most physics textbooks, static refers to forces
exerted on bodies at rest. As the racers leave the
starting line, both the wheels and the rest of the
racing cars are in motion. thus, static friction would
not apply at all to the situation as described.
The point of contact between tire and road is static
unless the wheels are slipping. The fact that the car is
moving is irrelevant. The surfaces in contact are
momentarily at rest with respect to each other. Static
friction applies (you hope -- else you are out of
control). J. Epstein
I'm afraid this is just not true.
The spinning wheels AT THE STARTING LINE undergo kinetic
friction from the time that they start spinning until
that race car comes to a full stop at the end of the
drag race.
J. Epstein