Re: [Phys-l] Work done by Static Friction

["Dan Crowe" <Dan.Crowe@Loudoun.K12.VA.US>]

In a reference frame that is at rest relative to the ground, the bed of
the truck does positive work on the crate via the static friction force.
 At the same time, the crate does an equal amount of negative work on
the bed of the truck via static friction.  The positive work done on the
crate increases the kinetic energy of the crate; the negative work done
on the bed of the truck decreases the increase in kinetic energy of the
truck below what it would have been in the absence of the static
friction between the crate and the bed of the truck.

Daniel Crowe
Loudoun Academy of Science
dan.crowe@loudoun.k12.va.us
> > > RLAMONT@providence.edu 03/14/07 5:22 PM >>>
A crate sits on the bed of a flat-bed truck. The truck is initially at
rest and then moderately accelerates. The crate does not slide, but
simply follows the motion of the truck. Did the force of static friction
that accelerates the crate do any work?

I ask this because when a block is decelerated by kinetic friction, the
KE of the block decreases and the internal energy of the surfaces
involved increases. What is the energy transfer (or whatever your
favorite terminology) mechanism for the static friction example above?

Bob at PC