# Thread: Statics of rigid bodies

1. ## Statics of rigid bodies

Stuck on the enclosed question.

I have done the first part, taken moments about A, found P to be $2g cos 30$, or 17.0N to 3sf. I am taking $g$ as 9.8N btw.

What I can't do is the second part, find the magnitude of R. I know that there are reactions at R, horizontal and verticle, I am just having problems resolving them and then working out.

Any help would be greatly appreciated

Craig

2. Originally Posted by craig
Stuck on the enclosed question.

I have done the first part, taken moments about A, found P to be $2g cos 30$, or 17.0N to 3sf. I am taking $g$ as 9.8N btw.

What I can't do is the second part, find the magnitude of R. I know that there are reactions at R, horizontal and vertical, I am just having problems resolving them and then working out.
There are only three forces acting on the rod: the weight 4g, and the forces P and R. If the system is in equilibrium then these forces form a vector triangle, as in the attachment. You can find the magnitude of R by applying the cosine rule in this triangle.

3. Originally Posted by Opalg
There are only three forces acting on the rod: the weight 4g, and the forces P and R. If the system is in equilibrium then these forces form a vector triangle, as in the attachment. You can find the magnitude of R by applying the cosine rule in this triangle.
Thank you! Not thought/been taught to do it this way, it is a lot simpler than messing around with resolving forces