# Homework Help: Finding Components of Force

1. Nov 7, 2013

### NoobeAtPhysics

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

Force F acts perpendicular to the inclined plane ABC. Assume x0 = 2.32 m, y0 = 3.44 m, z0 = 2.94 m, and F = 459 N.
Determine the moment produced by F about point B; What are the x,y,z component.

2. Relevant equations

Cross Product

3. The attempt at a solution

A (0,0,2.94)
B (2.32,0,0)
C (0, 3.44,0)

rac = 3.44j -2.94k
rbc = -2.32i + 3.44j
rac x rbc = {10.1136,6.8208, 7.9808}

uf = [rab x rbc]/[magnitude]={0.693785,0.467901,0.547477}
F=459*uf = {318.545, 214.832, 251.112}
mb = rbc * F = {864.44, 582.997, -1593.75}

I am wrong. It has been hours. Any help would be great

Last edited: Nov 7, 2013
2. Nov 7, 2013

### SteamKing

Staff Emeritus
What is the definition of a moment vector in terms of the force vector and the radius vector?

3. Nov 7, 2013

### NoobeAtPhysics

Sorry can you explain further
thank you

4. Nov 7, 2013

### NoobeAtPhysics

Can someone spot out what I did wrong?

5. Nov 7, 2013

### gildomar

The Rab and Rbc vectors are right, and so is their cross product, as well as the unit vector in the direction of the force. But I got 318.447i + 214.766j + 251.292k for the force vector. Oddly enough, I got the same moment though. Is the x, y, and z components at the end supposed to be the answer?

Last edited: Nov 7, 2013
6. Nov 7, 2013

### Staff: Mentor

Shouldn't the moment be rbc x F?

7. Nov 7, 2013

### NoobeAtPhysics

Yeah that's what i did but I'm always wrong

8. Nov 7, 2013

### NoobeAtPhysics

And yes gildomar, the answer is the components

9. Nov 7, 2013

### NoobeAtPhysics

Wow, nevermind. I actually got it right.. I just kept on putting N instead of N*m.... im never taking physics again.

thanks anyway