How do I calculate maximum spring compression using the work-energy theorem?

[cantgetno]

Homework Statement

A (m)kg box moving at (v)m/s on a horizontal, frictionless surface runs into a light spring of force constant (k)N/m.
Use the work-energy theorem to find the maximum compression of the spring.

Homework Equations

kinetic energy=1/2 m v^2
Change in kinetic energy = work done
hookes law: KS=F
FS=Work done

The Attempt at a Solution

(k)s^2= 0.5 x (m) x (v)^2

s =[0.5(m)(v)^2 / (k)] ^1/2

OR if
1/2 (k)s^2 = Work

0.5 (k) s^2 = 0.5 x (m) x (v)^2
s ^2 =0.5(m)(v)^2 / 0.5(k)
s=[(m)(v)^2 / (k)]^1/2

 

[Doc Al]

OR if
1/2 (k)s^2 = Work

0.5 (k) s^2 = 0.5 x (m) x (v)^2
s ^2 =0.5(m)(v)^2 / 0.5(k)
s=[(m)(v)^2 / (k)]^1/2

That's the one you want. The energy stored in a spring is 1/2kx^2, not kx^2.

 

[cantgetno]

Thanks