Resultant and Moment Homework: Determine R & Moment about O

[LMW - Dk]

Homework Statement

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

Homework Equations

see the image.

The Attempt at a Solution

See the image.

 

[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!

 

[LMW - Dk]

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

 

[tiny-tim]

sorry, i didn't notice your third picture

your F_z36 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?​

 

[LMW - Dk]

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

 

[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.

 

[tiny-tim]

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.

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?)​