# Statics of rigid bodies

• Apr 15th 2009, 05:51 AM
craig
Statics of rigid bodies
Stuck on the enclosed question.

I have done the first part, taken moments about A, found P to be \$\displaystyle 2g cos 30\$, or 17.0N to 3sf. I am taking \$\displaystyle 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 :)
• Apr 15th 2009, 11:29 AM
Opalg
Quote:

Originally Posted by craig
Stuck on the enclosed question.

I have done the first part, taken moments about A, found P to be \$\displaystyle 2g cos 30\$, or 17.0N to 3sf. I am taking \$\displaystyle 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.
• Apr 15th 2009, 01:51 PM
craig
Quote:

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 :)