Torque and static equilibrium beam with weights

AI Thread Summary
The discussion centers on a beam in static equilibrium with weights positioned at various points. The poster questions the answer key's assertion that the beam is in equilibrium, believing their calculations indicate a net torque of 1wL in the clockwise direction, suggesting it is not in equilibrium. Responses confirm that the poster's understanding is correct, and the answer key is likely incorrect. The importance of applying the equations of static equilibrium is emphasized, highlighting the need for accurate calculations in determining equilibrium status. Overall, the consensus is that the beam is not in equilibrium based on the provided weight distribution and torque analysis.
matermultorum
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Homework Statement


The answer is to be given in terms of L and w. The picture shows a beam of weight w and various blocks on it also each of weight w. It also shows the gravitational force acting downward on the center of gravity of the beam. The beam rests on a triangular pivot point.

2 blocks of weight w are stacked and sit 2L to the left of the pivot. 1 block sits 1L to the right of the pivot. The center of gravity force is also shown at 1L to the right of the pivot. Another block sits at 3 to the right of the pivot. I am to state why the beam is or is not in equilibrium.

Homework Equations


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The Attempt at a Solution


The answer key shows that it is in equilibrium. I don’t understand why it is. To me it seems that the spot that has the center of gravity will actually have a force of 2w at the center of gravity-one for the block and one for the beam. This gives -3wL + -2wL +4wL or a net torque of 1wL in the clockwise direction. Where am I thinking incorrectly about this? (I have only a small hope that I am right and the answer key is wrong).

Thank you!
 
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Why haven't you written the equations of static equilibrium to determine whether the beam is in equilibrium or not?
 
SteamKing said:
Why haven't you written the equations of static equilibrium to determine whether the beam is in equilibrium or not?
I thought that is what this is: -3wL + -2wL +4wL=-1wL and since it isn't zero, it isn't in equilibrium.
 
My EE degree son is home for the weekend and he thinks that I am right and the key is wrong. If you disagree please post.
 
matermultorum said:
This gives -3wL + -2wL +4wL or a net torque of 1wL in the clockwise direction. Where am I thinking incorrectly about this?
Assuming I understand your description of the problem, you are correct and the answer key is wrong.
 
Thank you!
 
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