# 2 blocks- Forces w/ friction

1. Oct 1, 2009

### mattmannmf

I have 2 blocks together: M1=3, M2=8

the friction of M1=6N, M2=16N
Force applied= 26 N

find total acceleration: ?
magnitude of force M1 to M2?
magnitude of acceleration for M1?
force magnictude from M2 to M1?

I know the following: M1 accel= M2 accel
I am going to combined the masses M1 & M2 together since accelerations are the same.
Here is my real question.. what do I do for the frictions? do I add the 2 frictions together? do I take the higher friction? I dont understand what to do for those.

I tried breaking it down to free body diagrams:

M1:
F(applied)+F1(moving forward)- F(friction of M1)- m1g= m1a

M2:
F1(moving foward)- F(friction M2) - m2g= m2a

Then i got this long formula:
Fapplied+ F(fr2)+m2g-Ffr1-m1g= a(m1-m2)

and i got acceleration to be -17? impossible..not sure where i went wrong

Last edited: Oct 1, 2009
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