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Re: Conservation of ME and nonconservative forces

I remember seeing the following argument about rolling
friction. Consider a wire which is bent and unbent many
times. Its temperature goes up. A rolling object is not
perfectly rigid; it is compressed and decompressed
constantly along diameters as they become parallel to
the normal reaction force. The so-called "internal
friction" is a dissipation mechanism to be considered.
Ludwik Kowalski
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William Beaty wrote:

On Wed, 27 Jun 2001, Paul O. Johnson wrote:

There is indeed no slipping, Oren, so there is no KINETIC friction. But
it seems to me that there must be STATIC friction to cause rolling. It
also seems to me that the instantaneous point of contact is indeed
moving down the plane, opposite to the static frictional force.
Therefore, the frictional force does negative work, converting
potential energy to thermal energy.

I don't know if it would be significant for something like a train, but
for small tabletop objects the ADHESION of the wheel with the table makes
a difference. Imagine trying to roll a steel ball across a glass
tabletop. Now imagine that the glass has a very thin coating of
half-dried rubber cement...

Also, if the rolling object and the flat surface are both insulators, then
as the object rolls along, we'd see "electrification by contact." The
rolling object would aquire a constantly increasing surface charge, and it
would leave behind a trail of opposite surface charge. Some of the
work going into the "rolling friction" would be stored as e-fields.

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