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I'm not sure whether Bob is saying static friction does or does not dowork in
his comment below. I suggest it does not, at least in the floor's frameof
reference. When I start to walk it always involves a leaning forward.In
this sense, my weight is providing a torque about my center of mass. Ipoint
believe that the frictional force, not doing work, is providing a pivot
for this torque. Am I wrong? However, I would not use this explanationin an
introductory course until torque is discussed. Is this another casewhere we
lead introductory students astray in that static friction does work andtexts I
accelerates objects, or am I completely wrong here? For example, most
have seen explain that when a person walks, they place a force back onthe
floor. By Newton's 3rd, they then say that the floor places a forceforward
on the person. In this explanation, the conclusion is that the staticfriction,
frictional force is causing the acceleration. But, if it is static
then how can it do work and cause the acceleration?same
Bob Carlson
In a message dated 12/18/98 9:10:40 PM Central Standard Time,
trebor@VELOCITY.NET writes:
The force of static friction in the rolling wheel performs much the
thefunction as does the force of static friction between your foot and
numberfloor when you walk. Think of a wheel as the limit of an infinite
of spokes, each with a shoe at its distal end!
And Martha Takats writes:
But I still worry about why
there are no non-conservative forces doing work--for example the force
of static friction, which prevents slipping. Can anyone give a SIMPLE
explanation of why we don't have to include it in the work-energy
equation?