The Naked Scientists
  • Login
  • Register
  • Podcasts
      • The Naked Scientists
      • eLife
      • Naked Genetics
      • Naked Astronomy
      • In short
      • Naked Neuroscience
      • Ask! The Naked Scientists
      • Question of the Week
      • Archive
      • Video
      • SUBSCRIBE to our Podcasts
  • Articles
      • Science News
      • Features
      • Interviews
      • Answers to Science Questions
  • Get Naked
      • Donate
      • Do an Experiment
      • Science Forum
      • Ask a Question
  • About
      • Meet the team
      • Our Sponsors
      • Site Map
      • Contact us

User menu

  • Login
  • Register
  • Home
  • Help
  • Search
  • Tags
  • Recent Topics
  • Login
  • Register
  1. Naked Science Forum
  2. On the Lighter Side
  3. New Theories
  4. Example where the energy is not conserved
« previous next »
  • Print
Pages: [1]   Go Down

Example where the energy is not conserved

  • 5 Replies
  • 2335 Views
  • 0 Tags

0 Members and 1 Guest are viewing this topic.

Offline LB7 (OP)

  • Sr. Member
  • ****
  • 454
  • Activity:
    0%
  • Thanked: 5 times
  • Ludovic Bavay Ubeda
Example where the energy is not conserved
« on: 29/08/2018 11:39:56 »
In the attached file
* eng.pdf (268.39 kB - downloaded 123 times.)
« Last Edit: 01/09/2018 13:57:54 by LB7 »
Logged
Ludovic Bavay 19011971 Valenciennes
 



Offline Bored chemist

  • Naked Science Forum GOD!
  • *******
  • 31101
  • Activity:
    11%
  • Thanked: 1291 times
Re: Example where the energy is not conserved
« Reply #1 on: 29/08/2018 12:02:48 »
You say "I study the sum of the energy during a deformation of a device, the device doesn’t return to the start
position. ".
The simplest example I can think of is a spring compressed and then tied with a string.
I can connect it to some apparatus and cut the string so the expanding spring drives a generator and get power from it.

But that's not "free energy" it's just using the energy that was put into the spring by compressing it.

It's nothing new, or very useful unless you can mine compressed springs or find a plant that grows them.
Logged
Please disregard all previous signatures.
 

Offline LB7 (OP)

  • Sr. Member
  • ****
  • 454
  • Activity:
    0%
  • Thanked: 5 times
  • Ludovic Bavay Ubeda
Re: Example where the energy is not conserved
« Reply #2 on: 29/08/2018 12:08:49 »
Quote from: Bored chemist on 29/08/2018 12:02:48
But that's not "free energy" it's just using the energy that was put into the spring by compressing it.

I counted the energy stored in the springs at start and at final:

- potential energy at start: -√2/2+(√2-1-d)S
- potential energy at final: +√2/2-√2/2*δ-((√2-1-d)S - (Sδ-Sdδ) )
« Last Edit: 29/08/2018 12:12:19 by LB7 »
Logged
Ludovic Bavay 19011971 Valenciennes
 

Offline LB7 (OP)

  • Sr. Member
  • ****
  • 454
  • Activity:
    0%
  • Thanked: 5 times
  • Ludovic Bavay Ubeda
Re: Example where the energy is not conserved
« Reply #3 on: 01/09/2018 13:58:37 »

Calculations:  with the depth of the device = 1 m, ‘S’ the surface of the white shape, ‘δ’ an infitisimal angle of rotation for the lateral walls, the black arm and the orientation of the springs:

Work to rotate the lateral walls:

-√2/2*δ


Work from the black arm:

+Sdδ

Work recovered to move out the white parts and move in the blue spheres:

The energy lost by the move out/in of the blue spheres is -δS-δdS*√S√2, the second term is very small in comparaison to the first. Note the move out/in in the direction of the attraction don't give/need energy what I lost in difference of pressure I win in difference of the length of the springs, the move out/in perpendicularly to the attraction have no difference of pressure but I need to increase the length of the springs

Potential energy lost by springs:

The difference of potential energy of the springs is
  - potential energy at start: -√2/2+(√2-1-d)S
  - potential energy at final: +√2/2-√2/2*δ-((√2-1-d)S – (√2Sδ-2Sdδ) )
  - the sum of potential energy of the springs is: -√2/2*δ+(√2Sδ-2dSδ)

The work won by the green line:

√2*δ-√2δS with S the surface of the white shape


The laterals walls rotate, so I need to move out/in :

I need to move out/in the volume (1+d+δ/2)*δ*√2*√2*√S
The mean of difference of pressure is √S/2

The energy recovered is (1+d+δ/2/√2)*δ*S   the term ‘δ/2/√2*δ*S’ is very small compared to the others


Sum of energy:

The sum is 0

« Last Edit: 01/09/2018 17:26:45 by LB7 »
Logged
Ludovic Bavay 19011971 Valenciennes
 

Offline Bored chemist

  • Naked Science Forum GOD!
  • *******
  • 31101
  • Activity:
    11%
  • Thanked: 1291 times
Re: Example where the energy is not conserved
« Reply #4 on: 01/09/2018 14:14:53 »
Quote from: Bored chemist on 29/08/2018 12:02:48
the device doesn’t return to the start
position. ".
That's the bit that matters.
If it doesn't return to the original condition then you haven't got a closed cycle from which you can repeatedly take energy.
It's like hydroelectric power- it only works because of rain.
Logged
Please disregard all previous signatures.
 



Offline LB7 (OP)

  • Sr. Member
  • ****
  • 454
  • Activity:
    0%
  • Thanked: 5 times
  • Ludovic Bavay Ubeda
Re: Example where the energy is not conserved
« Reply #5 on: 01/09/2018 15:01:46 »
Quote from: Bored chemist on 01/09/2018 14:14:53
Quote from: Bored chemist on 29/08/2018 12:02:48
the device doesn’t return to the start
position. ".
That's the bit that matters.
If it doesn't return to the original condition then you haven't got a closed cycle from which you can repeatedly take energy.
It's like hydroelectric power- it only works because of rain.

Even during a deformation, the sum of energy is conserved. I counted the potential energy stored at start and the potential energy recovered at final
« Last Edit: 01/09/2018 15:53:52 by LB7 »
Logged
Ludovic Bavay 19011971 Valenciennes
 



  • Print
Pages: [1]   Go Up
« previous next »
Tags:
 
There was an error while thanking
Thanking...
  • SMF 2.0.15 | SMF © 2017, Simple Machines
    Privacy Policy
    SMFAds for Free Forums
  • Naked Science Forum ©

Page created in 1.316 seconds with 42 queries.

  • Podcasts
  • Articles
  • Get Naked
  • About
  • Contact us
  • Advertise
  • Privacy Policy
  • Subscribe to newsletter
  • We love feedback

Follow us

cambridge_logo_footer.png

©The Naked Scientists® 2000–2017 | The Naked Scientists® and Naked Science® are registered trademarks created by Dr Chris Smith. Information presented on this website is the opinion of the individual contributors and does not reflect the general views of the administrators, editors, moderators, sponsors, Cambridge University or the public at large.