How Do You Calculate Friction Force in a Two-Mass System?

[-EquinoX-]

Homework Statement

http://img406.imageshack.us/img406/6092/testdd5.th.jpg http://g.imageshack.us/thpix.php


find the fk in terms of M,m,a

Homework Equations

The Attempt at a Solution

So what I got in the end result after decomposing the forces on each object and then do a substitution is :

fk = m(a+g) - Ma,

where m is the mass of the hanging block and M is the mass of the object in the plane. Is this wrong?

 

[Redbelly98]

I think your expression for T is incorrect. It may have to do with defining + and - directions.

In your +/- convention: if "a" is positive, do the blocks accelerate to the left & up, or to the right & down?