Two masses with friction and force

[nynja]

Homework Statement

Two blocks of masses m1 and m2 are placed on a table in contact with each other. The coefficient for friction u1 between m1 and the table, and between m2 and the table is u2. A horizontal force of magnitude F is applied to m1. We wish to find P, the magnitude of the contact force between the two blocks. Also find net force on m1, m2.

Homework Equations

F=ma
Fnet=ma
Ff = uFn

The Attempt at a Solution

I have tried to make fbd for both blocks and add up the forces but I am a little confused on how to make those. I have normal force pointing up for both, mg pointing down, and then it gets confusing as to which forces go which way on each mass. I came up with a solution of Fnet=ug(m1+m2) but this was incorrect. I want to understand this, not just let the answer be given to me.


First time posting let's see how this works :)

 

[lippyka]

The force applied to m1 will be equal to the force between the two blocks, P. The net force on m1 is thus F-P. To find the net force on m2, we need to consider the friction forces between each block and the table. The frictional force between m1 and the table is u1F, where F is the normal force between m1 and the table (equal to mg). Similarly, the frictional force between m2 and the table is u2F2, where F2 is the normal force between m2 and the table (equal to mg). Thus, the net force on m2 is P-u1F-u2F2. P = F - u1mg - u2mgFnet(m1) = F - PFnet(m2) = P - u1mg - u2mg