# Free body diagram drawing for a two force members on machine

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1. Jul 12, 2015

### lion_

1. The problem statement, all variables and given/known data
When a force of 2 lb is applied to the handles of the brad squeezer, it pulls in the smooth rod AB. Determine the force P exerted on each of the smooth brads at C and D

2. Relevant equations
$\sum F_x=0$
$\sum M=0$
$\sum F_y=0$

3. The attempt at a solution
I drew a free body diagram of Members EA with the initial force applied. Since A and B are two force members, $F_{AB}$ is drawn opposite direction in free body diagram BCD. However when I solve the the equations I get that P is opposite to the Free body diagram drawn. Why is that is there some mistake?

Moments about $E$ yields $M_E=2\cdot 2-F_{AB}=0$ so $F_{AB}=4$
In second FBD, I get that $P=-2$there must be some mistake in this?

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2. Jul 12, 2015

### Dr. Courtney

Wow, I thought I was the only one who ever used English/Imperial units any more.

The sum of the torques about a given axis must be zero.

Taks care, and carry your units along.