Equilibrium of Tilting Beam w/ Weight: Why does it Work?

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In summary, the conversation discusses the condition for a beam to start tilting when an object with a certain weight is attached to one end. The condition is that the moments must be exactly balanced, according to Newton's first law. The conversation also explores the idea that the beam can continue tilting even if the moments remain in balance.
  • #1
Fabian901
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Say I have a uniform beam supported by 2 bricks and I attach an object with a certain weight at one end of the beam so it starts tilting. Why is the beam still in equlibrium (sum of moments about one of the bricks is equal to 0) if it is tilting?. I've seen this exercise on youtube and I'm still not understanding it. The link is below if you want to have a look.

Thanks!
 
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  • #2
In the example, the condition being calculated is for the case that the beam is just about to tilt. The moments exactly balance, so Newtons first law applies.
 
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  • #3
Simon Bridge said:
In the example, the condition being calculated is for the case that the beam is just about to tilt. The moments exactly balance, so Newtons first law applies.
Okay, but does the weight on the edge have enough downward force to actually make it tilt or would I need to increase it? If it does have enough downward force to make it tilt then surely it is just a matter of seconds until the beam starts tilting and therefore the sum of moments would not equal 0.
Would this be correct or am I missing something?
 
  • #4
What does Newton's first law say?
If the beam is stationary, it remains stationary - if it is in motion, it stays in motion - at a constant (angular) velocity.

Lets say it (in the example) is stationary - then, with the moments exactly balanced the slightest extra moment, for the tiniest fraction of a second, will set it in motion at a constant angular velocity. You can see if the moments remain in balance while tilting by redrawing the picture with the beam tilted at some obvious angle, draw in the forces, and calculate the moments. However, they don't have to be out of balance for the beam to keep tilting.
 
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  • #5
Simon Bridge said:
What does Newton's first law say?
If the beam is stationary, it remains stationary - if it is in motion, it stays in motion - at a constant (angular) velocity.

Lets say it (in the example) is stationary - then, with the moments exactly balanced the slightest extra moment, for the tiniest fraction of a second, will set it in motion at a constant angular velocity. You can see if the moments remain in balance while tilting by redrawing the picture with the beam tilted at some obvious angle, draw in the forces, and calculate the moments. However, they don't have to be out of balance for the beam to keep tilting.
I see now! Thanks a lot for your help!
 
  • #6
No worries - the idea that you have to push something for it to move is a hard one to get rid of.
 
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1. How does the weight on one side of the beam create equilibrium?

The weight on one side of the beam creates a moment, or turning force, which is balanced by an equal and opposite moment from the weight on the other side of the beam. This results in a state of equilibrium where the beam remains stationary and does not tilt.

2. What factors affect the equilibrium of a tilting beam with weight?

The equilibrium of a tilting beam with weight is affected by the distance of the weight from the pivot point, the magnitude of the weight, and the angle at which the weight is applied. These factors determine the magnitude and direction of the moment created by the weight.

3. Why does the weight need to be placed at a specific distance from the pivot point?

The distance of the weight from the pivot point determines the length of the lever arm, which is the distance between the weight and the pivot point. The longer the lever arm, the greater the moment created by the weight and the more stable the equilibrium of the beam.

4. Is there a limit to how much weight can be applied to the beam before it tilts?

Yes, there is a limit to how much weight can be applied to the beam before it tilts. This limit is determined by the weight of the beam itself and the distance of the weight from the pivot point. If the weight applied exceeds this limit, the beam will tilt and the equilibrium will be disrupted.

5. How does the equilibrium of the tilting beam with weight relate to real-world applications?

The concept of equilibrium in a tilting beam with weight is applicable in many real-world scenarios, such as balancing a seesaw, a ladder against a wall, or a roof beam on supports. It is also important in engineering and construction, where structures must be designed to withstand and distribute weight in a way that maintains equilibrium and prevents collapse.

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