Compute Torque About Point A - 3 SF

[Peter2288]

[SOLVED] Torque Question

Homework Statement

See diagram for problem

additional instructions
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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

Homework Equations

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

The Attempt at a Solution

too many to name.

 

[WiFO215]

Homework Equations

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

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

 

[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.

 

[Doc Al]

For force 3, the r value is supposed to be the direct line between it and the point of pivot right?

Right.

Do I use the hypotenuse of the triangle for the r value?

Sure.

Also what angle do I use (arctan (3 / 4)??),

When using r F \sin\theta, the angle is the angle between the position vector and the force vector.

and am I supposed to somehow break up the force into x and y components?

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.)

 

[Peter2288]

Thanks guys.