Find the moment caused by all the forces

[385sk117]

Homework Statement

two couples are acting on the frame. If the resultant couple is to be zero, find the distance d

Homework Equations

The Attempt at a Solution

First find the point, Let's say A on the picture, and find the moment caused by all the forces
500cos30 x 0.9 acting downward, 500cos30 x (0.9+d) acting upward, moments by 750ns are cancelled, at least that was what i thinking but i don't think this is right method to use..
is moment by couple = f.d ?
so d = 1.8m?
i don't get this...
Please help me TT

 

[tiny-tim]

Hi 385sk117!

two couples are acting on the frame. If the resultant couple is to be zero, find the distance d
…
First find the point, Let's say A on the picture, and find the moment caused by all the forces
…

No, you don't need to choose a point …

the moment of a couple is the same about any point.

So just use your f.d formula for each couple separately.

 

[385sk117]

Thankyou :)