Re: Atwood's machine problem

[Dan Crowe <dcrowe@SOTC.ORG>]

An alternate perspective is to use the lever arm (moment arm) formalism.
The lever arm is the perpendicular distance from the origin to the line
of action of the force.  In this case, the lever arm equals the radius,
R, of the pulley.  The torque, T, equals the lever arm times the force,
F:

T = RF

which is nonzero.

Daniel Crowe
Oklahoma School of Science and Mathematics
Ardmore Regional Center
dcrowe@sotc.org
-----Original Message-----
From: Forum for Physics Educators [mailto:PHYS-L@list1.ucc.nau.edu] On
Behalf Of Herb Schulz
Sent: Monday, October 04, 2004 9:20 AM
To: PHYS-L@LISTS.NAU.EDU
Subject: Re: [PHYS-L] Atwood's machine problem

On 10/4/04 10:01 AM, "Ken Caviness" <caviness@SOUTHERN.EDU> wrote:

> I thought that I understood you, but perhaps I didn't.  Are you not
saying
> that
> the r vector points straight downward, from the pulley to the monkey?

Howdy,

The r vector points from the Pivot Point at the center of the Pulley
Wheel
while the CM of the Monkey hangs from a line which is tangent to the
Pulley's edge. This makes the component of r that is perpendicular to
the
velocity vector = radius of Pulley.

Good Luck,

Herb Schulz
(herbs@wideopenwest.com)