Re: [Phys-l] AP-B 2008

[Trevor Fink <tmfink@ilstu.edu>]

I'm no physics professor, so take what I say with a grain of salt...and note
that some of my terms may not be the standard terms.  I just like to take a
stab at things to see if I'm right.

It seems to me that all the potential energy in the spring is released as it
springs back (well call this velocity <--) towards its resting state.  As it
does this it transfers the energy into the string which, being tautly
connected to the block, accelerates the block.  Obviously the spring will
recoil (I think this the term?) and we will call this velocity -->  so more
or less the spring bounces back and forth until it eventually rests.  The
difference is the block is already accelerating at whatever rate in
direction <-- and the string is unable to transfer any energy in any
direction because it is no longer taut (thus isolating the two systems).
So, since there's no friction (ideally) the acceleration will remain
constant because the block is now acting independent of the spring system.
I've never seen one of these tracks in an experiment such as this, I wonder
how they keep the block from running over the string.  Maybe you know?

Again, this is not based on any type of mathematics, just what seems to make
sense to me and answered in layman's terms. I'm sure one of the more
educated members will be able to provide a more concise and sensible answer.

Trevor Fink


On 5/14/08 2:29 PM, "Kilmer, Skip" <kilmers@greenhill.org> wrote:

> Has anyone looked at this year's free response questions yet? I can't figure
> out how problem 2 can work. Why wouldn't whichever block is being pulled by
> the spring oscillate about an acceleration rather than accelerate at a
> constant rate?
> _______________________________________________
> Forum for Physics Educators
> Phys-l@carnot.physics.buffalo.edu
> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l