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## Homework Statement

See:

http://www.aapt.org/physicsteam/2010/upload/2010_FmaSolutions.pdf

#10

EDIT: There are several constants.

## Homework Equations

F = ma

Ff = μN

## The Attempt at a Solution

First: Draw a free-body diagram for block 2 (the bottom block)

Up: Normal force from floor pushing on block 2

Down: weight of block 1 on block 2

Down: weight of block 2 down

Right: Force F

Left: Force of Friction Ff

Up forces = Down forces

N = m1g + m2g

N = g(m1 + m2)

Ff = μg(m1+m2)

F_y = 0

F_x = F_net

so

Fnet = F - Ff

m2a = F - ug(m1+m2)

a = (F - ug(m1+m2)/ m2

This is the wrong answer.

The answer says it should be 2m1 + m2 not m1 + m2.

Why is this?

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