Re: Spring Problem Revisited

[Leigh Palmer <palmer@sfu.ca>]

> 	Good answers guys, I'm starting to see the light!  But, I'm still
> bothered by something.  Let me restate the problem another way.
> 	We have a horizontal, unstretched, Hookean spring connected at one end
> to a rigid support.  At the other end, I attach a mass m resting on a
> frictionless surface.  Now, I pull to the right on MASS m (not on the spring
> itself) with force F=kx.  The spring pulls back to the left on the MASS m (not
> on me) with force F=-kx.  Now, the sum of the horizontal forces acting ON THE
> MASS is 0.  NOW, how can the MASS (not the spring itself) ever accelerate?
> 	By the way, Donald Simanek came close to answering this in his post,
> but I'm wondering if anyone else has any insight.

I'm going to assume that you mean a massless Hookean spring. In that
case what I said about the (massive) spring itself still holds. You
will have to provide initial and terminal impulses (involving an
unbalanced force) to get the mass moving at a constant speed and to
stop it.

Leigh