Determine the distance of the center of gravity from the end X of the plank?

[looi76]

Homework Statement

A non-uniform plank of wood XY is 2.50m long and weighs 950N. Force-meters (spring balances) A and B are attached to the plank at a distance of 0.40m from each end, as illustrated in the Figure below

http://img266.imageshack.us/img266/2377/physicsp23bgh5.png​

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When the plank is horizontal, force-meter A records 570N

(i) Calculate the reading on force-meter B
(ii) Determine the distance of the center of gravity from the end X of the plank.

Homework Equations

Moment = Force x Perpendicular Distance

The Attempt at a Solution

(i) A + B = 950N
B = 950 - 570 = 380N

(ii) I don't know how to solve this question, need help!

 

[CompuChip]

In equilibrium, all the moments (A, B, gravity) cancel out.