Blocks with light springs

[jack1234]

Blocks with light springs (q31)

Hi, I have not idea how to do the following problem(all attempts failed):
http://tinyurl.com/28lahv

Can somebody help?

 

[catkin]

It might help if you showed what you have tried. See https://www.physicsforums.com/showthread.php?t=94379

 

[jack1234]

Sorry, I am not sure how to start the question with...just hope anyone can shed me some light.

 

[catkin]

OK. As a first step can you describe the energy transfer(s) that happen?

 

[jack1234]

Hi catkin, is it possible to give me enough information just to let me get started for this question?
Something like https://www.physicsforums.com/showthread.php?t=196130 or https://www.physicsforums.com/showthread.php?t=196166
I think this will be more helpful, thanks a lot:)

 

[learningphysics]

Use conservation of energy and conservation of momentum. remember the spring is light, so just assume its mass is 0.

 

[jack1234]

Got it, thanks:)
Followed is the working:
By conservation of momentum
0=3*2+2*v
v=3m/s
Potential energy stored in the spring
= sum of total kinetic energy
=0.5*2*(3)^2+0.5*3*(2)^2
=15J