Tensions with 3 blocks on a single pulley

[PAstudent]

Homework Statement

The diagram shows two blocks, each of mass m, connected by cord A, and the top block of mass m connected to the block of mass M by cord B. Both cords are of negligible mass. Cord B passes over a frictionless peg that is fixed in place. The system of blocks and cords is released from rest from the position shown, and because 2m<M, block M descends under constant acceleration the distance h in a time T. Derive, in terms of m, M, h, T, and the acceleration due of gravity g, expressions for the tensions in the cords A and B during that time T

[/B]

Homework Equations

The Attempt at a Solution

The picture shows my work. And I was wondering if I drew the FBD correctly and my equations were correct[/B]

 

[Doc Al]

(1) In your FBD for mass 2, you left out the tension from the cord below it.
(2) When writing your equations, take care to use a consistent sign convention for the acceleration.

 

[PAstudent]

So tension A= m(a+g)
And
Tension B= M(g-a)

 

[Doc Al]

So tension A= m(a+g)
And
Tension B= M(g-a)

Those are correct.