Re: torque

["C. Locke" <clocke@snet.net>]

Huw Powell wrote 
> of course the fly in the ointment is that the nice pretty little
> equations (like F=ma) I remember from early physics courses are
> operative only in a frictionless universe... been there but came back,
> kept dropping my coffee, forgot to recalibrate my assumptions...
> 
> in "reality" F = ma + some other term which reflects heat lost to
> friction (I presume in your example I will have at least warmed up the
> concrete block a tiny bit), or tied up temporarily as potential energy
> in the elasticity of the components in the system.  ("grunt in" = "grunt
> out" - "sweat")
>
No fly in the ointment, F=MA in a friction world.  F= the sum of all FA,
including friction.  And, if the concrete block didn't move, no heat. 
You have to overcome static friction before dynamic friction produces
heat.  And the force of friction on a moving object is mu N (frictional
coefficient times normal force) which is added (negative remember) to
the block mass times acceleration.  

chris locke 86 4kcstq