# Homework Help: Torque Question

1. Jan 14, 2008

### Peter2288

[SOLVED] Torque Question

1. The problem statement, all variables and given/known data

See diagram for problem

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For each of the three forces shown, compute the moment (N m, + CCW) about point A. Assume 3 SF for all numbers.

I am trying to solve for the moment(torque) of F3

2. Relevant equations

Force * (Distance between force and point A) * sine(theta)??

3. The attempt at a solution

too many to name.

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2. Jan 15, 2008

### WiFO215

That's it! Problem over right there. Tounet = F.r.sinX. Add the torques seperately, one by one.

3. Jan 15, 2008

### Peter2288

For force 3, the r value is supposed to be the direct line between it and the point of pivot right? Do I use the hypotenuse of the triangle for the r value? Also what angle do I use (arctan (3 / 4)??), and am I supposed to somehow break up the force into x and y components? I've tried some of this stuff, but none of it seemed to work. Thanks for your time.

Last edited: Jan 15, 2008
4. Jan 15, 2008

### Staff: Mentor

Right.
Sure.
When using $r F \sin\theta$, the angle is the angle between the position vector and the force vector.
You can always break a force into its components and then find the torque for each component and add them. (That would be much quicker, especially if you realize that $r \sin\theta$ is the perpendicular distance to the line of the force.)

5. Jan 15, 2008

Thanks guys.