# Physics

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Two blocks of masses M and 5M are placed on a horizontal, frictionless surface. A light spring is attached to one of them, and the blocks are pushed together with the spring between them, as seen in the figure below:

img404.imageshack.us/img404/8349/sbpic0906.png

1) A cord initially holding the blocks together is burned; after this the block of mass 5M moves to the right with a speed of v1=2.26 m/s. What is the velocity of the block of mass M?

I found the answer for this to be -11.3 m/s (which is correct).

2) Calculate the original elastic energy in the spring if M = 0.340 kg.

I don't know how to do this one! please help. I tried using 1/2mv1^2 + 1/2mv2^2 but no luck :(

• Physics -

Nevermind I figured it out... :)

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