# I Force-couple system equivalence: 3 moment equations

1. Jan 11, 2018

### Conductivity

In force-couple system equivalence, We can show that two systems are equivalent if the resultant force in both are equal and that it has the same line of action.

So Rx1 = Rx2, Ry1= Ry2, Ma1 = Ma2

Now my book says we can use another form of equation: We can choose 3 point and find the moment about them and use it to find the equivalent force, as long as a, b and c are not on the same line

I fail to see why should this work.
Ma = x Ry -y Rx
Mb = x Ry - y Rx
Mc = x Ry - y Rx

THe x and ys in each equation is different, How do you solve such a system to find Ry and Rx and the line of action? You can also use 2 moments and 1 resultant force equation in x or y direction

2. Jan 16, 2018

### PF_Help_Bot

Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.