Re: [Phys-l] 'Torque' question

[chuck britton <cvbritton@mac.com>]

At 9:33 PM -0400 7/11/10, Fakhruddin, Hasan wrote:
> Greetings folks!
> Say a force is applied on an object to rotate it about a hinge.  Why 
> does it get easier (like needing less force) to rotate the object as 
> the force is applied farther from the hinge?
> ~ Hasan Fakhruddin

Another approach to this question - one that is often useful for 
beginning students taking tests.

What is it that is constant in this problem????
Energy? Momentum? Angular Momentum?
But there is no continuing motion implied here - so maybe something 
else is 'constant'.

How about the 'Title' of the problem?
Torque?  = r x F


'further from the hinge' => r getting bigger.
r getting bigger => F getting less  (if torque stays the same).

HS students want to learn to take tests (as well as learning a bit of 
physics perhaps).