Re: PHYS-L Digest - 13 Sep 2002 - Special issue (#2002-406)

["John S. Denker" <jsd@MONMOUTH.COM>]

"Carl E. Mungan" wrote:
> Free-body diagram. The net force on the block is -umg. This equals
> ma. Thus a = -ug which is a constant. Thus we can use the equation of
> kinematics, v^2 = v0^2 + 2ax. But v = 0.

I recognize that as an equation from point-particle
kinematics.  If you claim it applies to objects with
nontrivial internal structure, please provide a
derivation or a pointer to a derivation.

Hint:  I've got a pocketful of counterexamples, so
any such derivation is going to be quite a rare bird.

>  We insist there is a logically sound theorem
> applicable to the block as a whole.

I'm from Missouri.  Show me.

> We can agree there is a problem
> of what to *name* various items.

I am not interested in quibbling about names.
I haven't raised the naming issue.
I agree we shouldn't go there now.

> That's fine and I have no problems with your personal preferences.
> "De gustibus non disputatum."

Since when is the definition of kinetic energy a
matter of personal preference?  The attempted
calculation in the previous note miscalculated
the kinetic energy by roughly a factor of two.

I don't see how a logically sound theorem could
produce such a result.