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Re: spin & direction of curve

This is the first description of direction of curve and direction of spin
that I have seen that makes sense.

I emphasize that we must first agree on what we are speaking about before we
can use any logic to come to any conclusion. Frequently the problems with
our discussions with students is that we are talking about one set of
conditions and they are interpreting it as something else.


Look at the ball along the axis of the spin. Say the ball is spinning
counter-clockwise. Now I'll draw the spinning ball (with little arrows)
and the trajectory (moving towards the top of the screen). Then we have:

Ball curving in Ball curving opposite
direction of spin: the direction of spin:
\ /
\ /
| |
\ /
| |
| |

< <
v O ^ v O ^
> >

This can, actually, be well described in terms of the right-hand rule. In
both cases omega (w) of the spin is pointing out of the screen. In the
first case, the Omega (W) of the curve is also pointing out of the screen
(with a varying magnitude); W is 'in the direction of' w. In the second
case, W is into the screen, in the opposite direction of w.

--
--James McLean
jmclean@chem.ucsd.edu
post doc
UCSD

Jim Riley, Department of Physics
Drury College
Springfield, MO 65802
e-mail: jriley@lib.drury.edu
Phone: (407) 873 7233