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## Homework Statement

The figure shows 3 crates being pushed over a concrete floor by a horizontal force f of magnitude 440N. The masses of the crates are m1=30 kg, m2=10kg, and m3=20kg. The coefficient of kinetic friction between the floor and each of the crates is 0.7. what is the magnitude F32 of the force on crate 3 from crate 2? (a picture is attached)

## Homework Equations

F=ma

F_x=ma_x

F-f_k=(m1+m2+m3)a_x

f_k=μ(m1 + m2 + m3)g

## The Attempt at a Solution

I solved for acceleration. my formula for acceleration is attached. hehehe. (oh, by the by, that formula is supposed to have "g" multiplied to the mu in the numerator). I got 0.473 m/s^2 for my acceleration. I read somewhere that to get F32, I should multiply the acceleration with m3. Somehow, that doesn't seem right to me. I ended up drawing a picture with space in between each crate. And F32 I conjured up to equal f_k (the kinetic force of friction) + F12 (force on crate 1 from crate 2) + m2*a_x. I then got a value of 402.12 N.

F32 = f_k + F12 + m2*a_x = 402.12 N

I am really lost. Please help me