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## Homework Statement

Two blocks have a spring compressed between them, Block A (mass 1kg) and block B (mass 3kg) . The spring has force constant 720 N>m and is

initially compressed 0.225 m from its original length. For each

block, what is (a) the acceleration just after the blocks are released;

(b) the final speed after the blocks leave the spring?

## Homework Equations

Fspring = kx = ma

1/2kx^2 = 1/2 mv^2

## The Attempt at a Solution

For a I got

Aa = 162m/s^2

Ab = 54m/s^2

However I cannot for the life of me figure out b. I have tried using kinematic equations and conservation of energy.

1/2(720N)(0.225)^2 = 1/2(1kg)(v)^2

Gives me 6.03m/s for the 1kg mass

and 3.4m/s for the 3kg mass.

I know these results are wrong. They are supposed to be 5.23m/s and 1.74m/s

Thanks