Science Fair - Why perpertual motion won't work.

[cookiepoppers]

Hi,

I am thinking of doing my next science fair project on perpetual motion, showing what prevents it from working. I am thinking of getting a 1-2 foot diameter plastic tube, maybe 3 feet long, mounting one electric fan about 1 foot inside one end, and another unpowered fan one foot inside the tube from the other end. My idea would be to connect a generator to the unpowered fan so that the powered fan would blow, spin the unpowered fan, and generated some power. I would discuss the reasons that the powered fan, spinning the unpowered fan, can't generated more power than it takes to run the system.

I won't be able to start my project until my birthday, when I can buy the materials, but I have some questions. I don't want to do this unless I can show that the power generated is somewhat close to the input power. I mean, it won't make sense if the output is 70% of the input. Can anyone tell me if this idea could end up outputting at least 90% of the input power, without having to buy some uber expensive fans and generators?


Thankies,

JM

 

[cepheid]

Welcome to PF,

some power. I would discuss the reasons that the powered fan, spinning the unpowered fan, can't generated more power than it takes to run the system.

Okay. So basically you want to demonstrate the conservation of energy. The energy you get out can't be greater than the energy you put in.

I don't want to do this unless I can show that the power generated is somewhat close to the input power. I mean, it won't make sense if the output is 70% of the input.

What won't make sense?

 

[cookiepoppers]

Not that it would not make sense, just that I would rather have the project result in over 90%. I appreciate the reply but you did not answer my question.

JM

 

[cepheid]

Not that it would not make sense, just that I would rather have the project result in over 90%. I appreciate the reply but you did not answer my question.

JM

Yeah, I get that you want a result of over 90% efficiency, but I'm just trying to understand your motivation for that. Why does it matter? How is it important to illustrating your point?

Off the top of my head, I don't know the answer to your question. However, if I had to guess, I'd think that achieving 90% efficiency would be unlikely with such a setup.

 

[asteriatic]

Dear JM,

Thank you for sharing your idea for a science fair project on perpetual motion. While it may seem like a fascinating concept, perpetual motion machines are not possible according to the laws of thermodynamics. The first law states that energy cannot be created or destroyed, only transformed from one form to another. This means that the energy generated by the powered fan will always be equal to or less than the energy needed to run the system. The second law states that in any energy conversion, there will always be some energy lost as heat. This means that even if your system were to output 90% of the input power, it would still not be considered a perpetual motion machine.

Your proposed experiment is a good way to demonstrate these principles. However, it is important to note that the efficiency of your system will depend on the quality of the fans and generator you use. Cheaper fans and generators may not be as efficient and could result in a lower output compared to the input. It is also important to consider other factors such as friction and air resistance, which could further decrease the efficiency of your system.

I encourage you to continue with your project and to explore the reasons why perpetual motion is not possible. It is a great opportunity to learn about the laws of thermodynamics and the limitations of energy conversion. Best of luck with your project!

Sincerely,