Block hits block with spring. COE and COM

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SUMMARY

The discussion focuses on a physics problem involving two blocks and a spring, specifically addressing the maximum compression of the spring, final velocities after collision, and the nature of the collision. The first block, with a mass of 3.0 kg and an initial velocity of 8.0 m/s, collides with a stationary 4.5 kg block attached to a spring with a spring constant of 720 N/m. The analysis confirms that the collision is elastic, meaning both momentum and kinetic energy are conserved throughout the interaction.

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I'm doing the same problem as in this thread: https://www.physicsforums.com/showthread.php?t=70219

Homework Statement


A 3.0 kg block slides along a frictionless tabletop at 8.0 m/s toward a second block (at rest) of mass 4.5 kg. A coil spring, which obeys Hooke's law and has spring constant k = 720 N/m, is attached to the second block in such a way that it will be compressed when struck by the moving block

a. what will be the maximum compression of the spring?
b. what are the final velocities of the blocks after collision?
c. is the collision elastic or inelastic?

Homework Equations



I guessed at c and it's elastic, so both momentum and kinetic energy are conserved

COM: mAv0A=mAvFA+mBvFB

COE:
1/2mAv0A^2=1/2mAvFA^2+1/2mBv)B^2

Potential spring energy= 1/2kx^2

The Attempt at a Solution



a.I tried setting the spring potential energy and kinetic energy of mass A equal, but that doesn't work. I don't really know how to work with springs...
b.I tried solving the system of equations that's in the other thread, but I go something like x=0, so something is wrong there
c.it's elastic. yay =D
 
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