Equilibrium: Brick on Cylinders

[ArticMage]

Homework Statement

http://img143.imageshack.us/img143/589/showmepl.gif

The above figure shows a large, uniform brick supported on two cylinders L and R so that it is exactly horizontal. The areas of the two cylinders are related such that AL = 2.1AR. The Young's moduli of the two cylinders area related such that EL = 2.8ER. The two cylinders had exactly the same length before the brick was placed on them.
a)What fraction of the bricks weight is supported by the left cylinder?
b)What fraction of the bricks weight is supported by the right cylinder?
c)What ratio of the distance from the center of mass of the brick to the center lines of the two cylinders?

Homework Equations

F/A=E*dL/L

The Attempt at a Solution

So for a and b I get F1 = 2.8 Er*2.1Ar*dL/L and F2= Er*Ar*dL/L then do F2/F1 or F1/F2 i end up with 1/(2.8*2.1) as everything else cancels. This is the correct answer for part c. So I'm not really sure what's happening here.

 

[ideasrule]

So for a and b I get F1 = 2.8 Er*2.1Ar*dL/L and F2= Er*Ar*dL/L then do F2/F1 or F1/F2 i end up with 1/(2.8*2.1) as everything else cancels. This is the correct answer for part c. So I'm not really sure what's happening here.

Draw a free-body diagram on the mass and write out Newton's rotational second law. This, plus the expressions you've already found, should be enough to solve the problem.

For the force, you want to find F1/(F1+F2) and F2/(F1+F2), because due to Newton's second law, F1+F2 must be the weight of the block.