# Thread: Determine the distance of the center of gravity from the end X of the plank

1. ## Determine the distance of the center of gravity from the end X of the plank

Question:
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

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.

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

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

2. Originally Posted by looi76
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(ii) I don't know how to solve this question, need help![/SIZE][/FONT]
I've modified your drawing a little bit.

Use momenti. The turning point of the plank is the point at forcemeter B:

$970\ N \cdot x = 570\ N \cdot 1.7\ m~\implies~x \approx 0.998969...\ m \approx 1\ m$

Therefore the center of mass is 1.4 m from the endpoint Y that means it is 1.1 m from the endpoint X.