Exploring the Law of Conservation of Energy with a 5kg Weight and 10L Bucket

In summary, the conversation discusses a question about the law of conservation of energy and the possibility of using an air pump to produce electric energy. The question involves a weight at the bottom of a lake and an upside down bucket attached to it, and whether the energy used by the air pump is equal to or greater than the energy needed to pull the weight up. The conversation also mentions a thread on perpetual motion machines and notes that the thread is closed for now.
  • #1
tiago000000
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Hi everyone! I regularly use the forum to learn but never registered to post anything, as I have nothing to teach really…
But today I have a question regarding the law of conservation of energy that I can’t find the answer to, and maybe someone will help me understand:

(I’ve attached a drawing)
Say we have a weight of 5kg at the bottom of a lake (11m deep), and an upside down 10L bucket above it attached to it by a few strings (9m deep). I then have an efficient air pump above the water line that pumps roughly 20L (I think, because of how it compresses down there) into the bucket and the whole apparatus comes up to the surface.

My question is: is the amount of energy used by the air pump equal/greater than the energy that would be needed to pull the same weight to the same place, or would it be possible for it to be smaller?

And if it was possible to use less energy to pump air down than it would be to pull the weight up, could you use this same principle to produce electric energy?

Ironically, as I’m waiting for the picture to upload, I’ve noticed a thread titled “why we don’t discuss perpetual motion machines”

Thank you everyone and I’m sorry for such a long post!
 

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  • #2
tiago000000 said:
Ironically, as I’m waiting for the picture to upload, I’ve noticed a thread titled “why we don’t discuss perpetual motion machines”
Yup.

tiago000000 said:
And if it was possible to use less energy to pump air down than it would be to pull the weight up, could you use this same principle to produce electric energy?
Nope.

tiago000000 said:
My question is: is the amount of energy used by the air pump equal/greater than the energy that would be needed to pull the same weight to the same place, or would it be possible for it to be smaller?
The energy to drive the pump will be equal to or greater than the change in gravitational potential energy (GPE) that the mass gained in being lifted to the surface.

As you noted, we don't discuss PMMs or over-unity mechanisms. Thread is closed for now.
 
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Related to Exploring the Law of Conservation of Energy with a 5kg Weight and 10L Bucket

What is the Law of Conservation of Energy?

The Law of Conservation of Energy states that energy cannot be created or destroyed, but can only be transferred or transformed from one form to another.

How can the Law of Conservation of Energy be explored with a 5kg weight and 10L bucket?

By performing an experiment where the 5kg weight is dropped into the 10L bucket from a certain height, the potential energy of the weight is converted into kinetic energy as it falls. This energy is then transferred to the water in the bucket, causing it to splash and create waves. This demonstrates the conservation of energy as the total amount of energy remains the same throughout the process.

What is the relationship between potential and kinetic energy in this experiment?

In this experiment, potential energy is converted into kinetic energy as the weight falls into the bucket. The higher the starting height of the weight, the more potential energy it has, and therefore, the higher the kinetic energy it will have when it reaches the bottom of the bucket.

What factors can affect the outcome of this experiment?

The height from which the weight is dropped, the mass of the weight, the volume of water in the bucket, and the type of surface the bucket is placed on can all affect the outcome of the experiment. Additionally, external factors such as air resistance and friction can also play a role.

How does this experiment relate to real-life applications of the Law of Conservation of Energy?

This experiment is a simplified version of real-life scenarios where energy is transformed and transferred from one form to another. For example, when a rollercoaster goes down a hill, the potential energy at the top is converted into kinetic energy as it goes down, and then the kinetic energy is transferred to the brakes to stop the rollercoaster. This demonstrates the Law of Conservation of Energy in action.

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