Re: [Phys-l] AP-B 2008

["Josh GATES" <jgates@sbschool.org>]

If the blocks had started from rest, you'd be right.  However, the problem
states that both blocks are initially comoving and coaccelerating.  If you
look at the forces on each of the blocks (2 on the block being pulled, 1
on the other), you can see that this is a possible and stable state.  

If your kids are conceptually savvy, they'll recognize that the first
question can be solved by disregarding the internal forces - by treating
the two blocks as one.

Josh Gates
Stoneleigh-Burnham School
Greenfield MA

Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
> 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?
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