# Resultant and moment

1. Sep 20, 2013

### LMW - Dk

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

I have to determine the resultant R and the moment about O.

2. Relevant equations

see the image.

3. The attempt at a solution

See the image.

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• ###### Udklip.PNG
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2. Sep 21, 2013

### tiny-tim

Hi LMW - Dk! Welcome to PF!

Show us what you've tried and where you're stuck, and then we'll know how to help!

3. Sep 21, 2013

### LMW - Dk

See the pictures. I have found the moment and the resultant. However I think it's the wrong method ^^

4. Sep 21, 2013

### tiny-tim

sorry, i didn't notice your third picture

your Fz36 should be minus 36, shouldn't it?

(btw, i think most people find it easier to use cos and sin, of angles < 90°, and then use common-sense to decide whether its + or -)

i don't understand what you did to find the moment
can you please type it out in the post?​

5. Sep 21, 2013

### LMW - Dk

Well can't you tell me how you would do this problem? how would you find the resultant and the moment?

6. Sep 21, 2013

### LMW - Dk

If you click on the second picture then you can see that i have drawn a direction vector. Then i have found the cfross product of the direction vector and the resultant force.

7. Sep 21, 2013

### tiny-tim

ah, now i understand …

no, you've crossed the resultant with the position vector for only one of the vectors: you need to cross each vector with its own position vector, and then add (ie, there's no short-cut)

(and did the minus 36 help?)​