http://img820.imageshack.us/img820/277/avjv.png
The weight of block A is 250N. The block is static and the spring (k =17 kN/m) has its natural length at the moment the block A starts it's movement downward. Find the velocity of block A when it has traveled 0.9 m and the max distance it will travel from its original place.

I tried this

Newton's 2nd law of block A
-T + W(A) = m(A)a(A)

Then at the B pole
2T - Fr = 0
T = Fr/2
T= k (delta x)/2
Since T changes as the spring is pulled
dT/dx = k/2

Replacing that on my block A equation
I end up getting a negative speed of A :/

Question

http://img820.imageshack.us/img820/277/avjv.png
The weight of block A is 250N. The block is static and the spring (k =17 kN/m) has its natural length at the moment the block A starts it's movement downward. Find the velocity of block A when it has traveled 0.9 m and the max distance it will travel from its original place.

I tried this

Newton's 2nd law of block A
-T + W(A) = m(A)a(A)

Then at the B pole
2T - Fr = 0  
T = Fr/2
T= k (delta x)/2
Since T changes as the spring is pulled
dT/dx = k/2

Replacing that on my block A equation
I end up getting a negative speed of A :/