Re: [Phys-l] Queston: simple pendulum lengthen suspension.

["Jeffrey Schnick" <JSchnick@Anselm.Edu>]

In my earlier analysis, I assumed that the pivot point was a fixed point
in space.  If, in increasing the length of the pendulum we keep the
position of the bob fixed and move the pivot point, the answer and the
reason are the same as before in the case of the length increasing at
maximum displacement from equilibrium.

If we move the pivot up when the bob is at its equilibrium position, we
again (as for the fixed pivot case) find that the new amplitude (maximum
angular displacement from equilibrium) is less than the amplitude for
the shorter pendulum. See
<http://www.anselm.edu/internet/physics/phys-l/pendulum.gif>

The answer to BC's question:
> U = mgh = mgl(1- cos A)
>
> If l is longer, then A should be smaller???

is yes.

Jeff Schnick 

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of R. McDermott
> Sent: Sunday, March 18, 2007 7:52 AM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] Queston: simple pendulum lengthen suspension.
>
> Reading Jeff S' reply, the 'A' in the equation is 'theta', not
> amplitude?
> Always a danger to jumping into something in the middle; the word
> 'amplitude' used in conjunction with an equation with 'A' in it led me
> astray.  Sorry for my distracting response earlier.  I agree
> completely with
> Jeff's analysis.
>
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