How Do You Calculate Forces on a Plank with Unevenly Placed Weights?

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To calculate the forces acting on a plank with unevenly placed weights, the turning effect equation is used, where the force is multiplied by the distance from the pivot. In this scenario, a uniform plank weighing 120 N supports an 80 N weight placed midway between two stools. The calculated forces on stools A and B were initially found to be 88 N and 112 N, respectively. However, the correct answers are 80 N for stool A and 120 N for stool B, indicating a misunderstanding in the distance used in calculations. Accurate application of the moment equation is crucial for determining the correct forces.
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Moment -- A weight on a plank

Homework Statement



A uniform plank of weight 120 N rests on two stools as shown in the link provided below. A weight of 80N is placed on the plank, midway between the stools. Calculate the force acting on the stool at A and B. The answer is 80N and 120 N respectively. I calculated the answers to 88N and 112N.

The image link : http://imageshack.us/photo/my-images/864/moments.png/


Homework Equations



Turning effect = Force * Distance from the pivot

The Attempt at a Solution



(80*1.25) + (120*1.5) = FB * 2.5
FB = 112N

(80*1.25) + (120*1.0) = FA * 2.5
FA = 88N
 
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welcome to pf!

hi psychicgerm! welcome to pf! :smile:
psychicgerm said:
(80*1.25) + (120*1.5) = FB * 2.5
FB = 112N

(80*1.25) + (120*1.0) = FA * 2.5
FA = 88N

it isn't 1.25 :wink:
 
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