Determining an expression for acceleration

[kobylorat]

Homework Statement

Here is the question: http://i1110.photobucket.com/albums/h459/granolup/Untitled.png

It is assumed that the blocks are not moving.

Homework Equations

F=ma
N=mg
friction = umg

The Attempt at a Solution

I have started out drawing free-body diagrams for each of the three wedges.
For m1, there is a force due to gravity pointing downwards, a normal force pointing to the top right.
For m2, there is a force due to gravity pointing downwards, a normal force pointing to the bottom left, and the force of kinetic friction pointing to the top left.
For m3, there is a force due to gravity pointing downards, and a normal force pointing upwards.

 

[tiny-tim]

welcome to pf!

hi kobylorat! welcome to pf!

I have started out drawing free-body diagrams for each of the three wedges.
For m1, there is a force due to gravity pointing downwards, a normal force pointing to the top right.
For m2, there is a force due to gravity pointing downwards, a normal force pointing to the bottom left, and the force of kinetic friction pointing to the top left.
For m3, there is a force due to gravity pointing downards, and a normal force pointing upwards.

ok so far (but isn't there also a friction force from the ground, and between 2 and 3?) …

now write out the equations of motion, including a purely geometric equation which specifies that block 2 stays on block 1 ​