Re: torque

[Robert Myers <rmyers@inetone.net>]

>well, I don't know about torque, but force requires motion for it's
>definition - there is no acceleration without motion, or at least a
>change in the rate of it.  relatively speaking anyway....

I think you are a little off on this one, Huw.  Force can and does exist
without acceleration.  Imagine a block of concrete sitting on the ground.
You push on it from the right.  You are exerting a force of some amount
(let's say 100 pounds for simplicity).  Why doesn't the block move?
Because the force of friction is "pushing" on the block with a force of 100
pounds in the opposite direction.  What do you do to get the block to move?
 Push harder until the force you are applying overcomes the maximum force
from friction (which is related to the weight of the object and the
coefficient of friction between the object and what it's sitting on).

Now Work is a different matter.  Work = force X distance.  If the object
just sits there and doesn't move then no matter how hard you push on it you
have done no work (regardless of the "evidence" of the sweat upon your brow).

Torque is like force.  In fact it is defined as force X lever arm.  With a
non-zero lever arm, rotation will happen only when sufficient torque is
applied to overcome resistive (frictional?) forces.

There is a force of gravity operating on the beer you hold in your hand.
Why doesn't the beer fall into your lap (assuming you're sober, of course,
:-) )?  You are applying an equal force upwards to counteract the force of
gravity.  :-)


___
   Bob
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