Combination W-K problem with spring

[itsvt2013]

Homework Statement

The 2 Kg slider A is held at rest against the spring k=900 compressing the spring by 0.4m. It is released and slides down the 5 m long ramp. Friction is negligible along the track. Slider A then makes an elsastic collision with the 3Kg slider B that is initially at rest. Find the velocity of slider B right after the collision.

Homework Equations

I used w-k equation then elastic collision to find V'B

The Attempt at a Solution

The answer suppose to be 8.8

 

[jdc15]

Start by using the formulas for energy stored in a spring and kinetic energy. Use these to calculate initial velocity. Then find out how much it accelerates down the ramp.