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# Re: are normal reaction and tension conservative ?

• From: "John S. Denker" <jsd@MONMOUTH.COM>
• Date: Sat, 30 Jun 2001 16:42:17 -0400

At 01:47 PM 6/30/01 -0400, Chuck Britton wrote:

Back in the late '60's, some dude named Goldstein had a text book on
Classical Mechanics

:-)

that left me with the IMPRESSION that any
velocity dependent force is non-conservative.

Almost any. A charge moving slowly through a constant magnetic field is
the obvious exception, because the force is normal to the velocity, as
Chuck noted:

When presenting magnetic forces (QvB) to neophytes we say that no
work is done since the force is normal to the displacement.

Right.

(When DOES the radiative component enter into our curriculum?)

Maybe when the charge moves more quickly?

I can also say the words 'holonomic(sp),

That constrains the system to a subspace of whatever state space it would

http://webug.physics.uiuc.edu/courses/phys326/spring01/lectures/lagrange_
http://webug.physics.uiuc.edu/courses/phys326/spring01/lectures/lagrange_2/t
sld003.htm

scleronimous(sp)

That's usually "scleronomic". Same as above, with the added feature that
the constraint equation has no explicit time-dependence.
http://www.aa.washington.edu/courses/aa571/notes4.pdf

As a rough analogy: in chess, the bishop is subject to a scleronomic
constraint (always red or always black); the knight's constraint is
non-scleronomic (alternating red and black) if we interpret "time" to be
the number of moves that piece has made.