block 1 follows block 2 on a frictionless surface. Block 2 has a spring attached behind it with

__spring constant=k=1100N/m.__

__Block1-> m1=4kg v1=20m/s__

Block2-> m2=10.0kg v2=6m/sBlock2-> m2=10.0kg v2=6m/s

The collision between the two is totally inelastic. And after the collision block1 and block2 move with

**v3=10m/s***How much does the spring compress?*

I tried finding the kinetic energy from block1 and then the kinetic energy after the collision. I thought the sum would give the amount of potential energy stored in the spring. And finding the distance with Epot=0.5*kx^2

The way I find the kinetic energy from block one is taking the relative velocity between the blocks-> 20m/s-6m/s=14m/s.

Then Ekin=0.54kg14^2

And Ekin2=0.5(m1+m2)(10m/s)^2

then Ekin2-Ekin=-308J

Solving for x with Epot=308J gives me a distance of 0.75m

The answer is supposedly 0.71m