M1 (aka, my worst nightmare) - Moments question

Could someone briefly explain to me how these questions work please? I'm sure they are very simple when you know how but I can't work it out from looking at my textbook examples/common sense!

A uniform bean AB of length 4m and mass 21kg has a particle of mass 15kg attatched to A and a particle of mass 18kg attatched to B. The beam is balanced horizontally on a single support at C. Find the distance AC?

Cheers,

--42

Reply 1

James

Draw a diagram, mark on the weights (A, B and the midpoint), and put C somewhere. Then call the distance of C from A "x". So the distance BC is 4-x, etc. Can you do it from here?

Reply 2

-42-

Cheers James, got it to be 2 and a ninth metres which was correct when I checked. So much easier with diagrams...I feel a bit stupid now so thanks for your patience!

--42

Reply 3

James

-42-

Cheers James, got it to be 2 and a ninth metres which was correct when I checked. So much easier with diagrams...I feel a bit stupid now so thanks for your patience!

No problem, I'm always happy to help. :smile:

Drawing a diagram is always a good idea in mechanics, even for the easier questions. It takes a few seconds, and makes it much easier to visualise what's going on.