"Find Tension Force Between Two Hanging Blocks

[usernametaken]

Homework Statement

A block is hanging from a rope which has another rope connected to another block underneath.
The top block has a mass of 60 Kg and the bottom block has a mass of 30 Kg. Both blocks are accelerated 1.2 m/s^2 upward. What is the tension force between the two blocks? (Assume rope is mass-less)

Homework Equations

F = ma

The Attempt at a Solution

I figured I could get the tension force of the top rope by combining both masses together.

F = ma = (90 Kg)(1.2 m/s^2) = 108 N
F = T - mg; => T = F + mg = 108N - (90 Kg)(9.80 m/s)
T = 990 N

I don't even know where to begin to find the tension force between the two blocks.

 

[rl.bhat]

Hi usernametaken, welcome to PF.

When the blocks are accelerating upward, the net acceleration is (a + g).
So F = (m1+m2)(a + g). And for m1
F - T = m1*a

Now find T.

 

[fizzynoob]

Sum of the forces in the why conclude:

Fy = T - (m1+mg)g = (m1+m2)a; T is uniform through out the system

therefor T = (m1+m2)(a+g)