Feyman and layman explanation of energy conservation

In summary, Feynman explains how some laws are not independent of energy conservation and that instead of using the law of levers, energy conservation can be used to determine the weight needed on one side for balance. He also addresses the confusion about potential energy and kinetic energy, stating that when a lever is balanced, there is no change in potential energy and therefore no kinetic energy is gained. He clarifies that in this scenario, the lever does not oscillate to the horizontal position, as there is no change in potential energy.
  • #1
AntiElephant
25
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Skip to 29:50. Here Feynman is explaining how some laws are not independent of energy conservation. In this case he goes on to explain how instead of using the law of levers were can use energy conservation to see what weight an object needs to on one side be to balance (or be in a state where is tilts back and forth without problems)

However I'm unsure how he comes to explain it. He seems to conclude that the potential energy at balance should be the same as the potential energy when it's titled. Why is this exactly? I thought it should be the total energy we need to worry about? Actually in an analogy previously it seems quite clear that only the total energy should be conserved. I probably wouldn't have worried about it except for the fact it also plops out the right answer, W = 8lb, so I must be understanding something wrong.

When it's tilted there is maximum potential energy, when it returns to balancing point some of the potential energy is now rotational kinetic energy. Right? How can the potential energy always stay zero?
 
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  • #2
His point is that when a lever is balanced it can very easily (i.e. by only adding enough energy to overcome friction) be rotated a small distance about the fulcrum. So as no energy has been added, the increase in potential energy of the mass that is raised at one end of the lever must equal the decrease of the PE in the mass that is lowered. It is assumed that the system is stationary before and after the rotation so that KE is zero.
 
  • #3
MrAnchovy said:
His point is that when a lever is balanced it can very easily (i.e. by only adding enough energy to overcome friction) be rotated a small distance about the fulcrum. So as no energy has been added, the increase in potential energy of the mass that is raised at one end of the lever must equal the decrease of the PE in the mass that is lowered. It is assumed that the system is stationary before and after the rotation so that KE is zero.

Okay. So when it oscillates to the horizontal position would we have to conclude that KE at this point is practically 0? Because if the PE is always 0 at all stages then it could not have gained any KE.
 
  • #4
AntiElephant said:
Okay. So when it oscillates to the horizontal position would we have to conclude that KE at this point is practically 0? Because if the PE is always 0 at all stages then it could not have gained any KE.
No, it does not oscillate to the horizontal position, it remains in the displaced position because there is no change in PE. Perhaps you are thinking about a balance rather than a simple lever where there is a counterweight that gains PE when the balance arm is displaced.
 

1. What is energy conservation?

Energy conservation is the principle that states that energy cannot be created or destroyed, but can only be converted from one form to another. This means that the total amount of energy in a closed system remains constant over time.

2. Who is Feynman and what is his explanation of energy conservation?

Richard Feynman was a Nobel Prize-winning physicist who made significant contributions to the field of quantum mechanics. His explanation of energy conservation is based on the laws of thermodynamics, specifically the first law which states that the total energy of a closed system is constant.

3. What is a layman's explanation of energy conservation?

A layman's explanation of energy conservation would be that energy cannot be created or destroyed, but can only change form. This means that energy can be transferred from one object to another, but the total amount of energy in the universe remains the same.

4. How does energy conservation impact our daily lives?

Energy conservation is important in our daily lives because it affects how we use and consume resources. By conserving energy, we can reduce our impact on the environment and save money on our energy bills. Additionally, understanding energy conservation can help us make more informed decisions about energy usage.

5. Are there any exceptions to the principle of energy conservation?

There are no known exceptions to the principle of energy conservation. However, in certain scenarios, it may seem like energy is being created or destroyed, when in reality it is just being transferred from one form to another. For example, in nuclear reactions, mass is converted into energy according to Einstein's famous equation, E=mc^2.

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