Re: MOMENT OF INERTIA

["Rauber, Joel Phys" <RAUBERJ@MG.SDSTATE.EDU>]

> Hmmm.  Consider the case of the block on a table, being accelerated by a
> string, say.  Now put a second block on top of the first.  The force that
> accelerates this second block is the force of friction that the first block
> exerts on the second.  Friction always opposes the motion, except when it
> doesn't.

Friction always opposes the *relative* motion (or impending motion); no
exceptions that I'm aware of.  In the above example the forward frictional
force of the bottom block on the top is opposed to the "impending" motion of
the top block, which would be backwards relative to the bottom block if
friction were turned off (dialed down to a minuscule value).

I hope I wrote the above the way I intended!

Joel