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Somebody wrote:

_________________

Back-of-the-envelope "Kinetic Energy Debunk"

Given:

[math]f=ma[/math]

and

[math] e=\cfrac{1}{2}mv^2 [/math]

then

[math]a=\cfrac{f}{m}[/math]

So if this device can produce a constant force then it will produce a constant acceleration.

BUT!... because Kinetic Energy is proportional to the SQUARE of velocity, and the energy being put in is constant, then at some time the attained velocity will mean there is more kinetic energy in the device than has been put in to the device. Yay, free energy!

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Hang on!!!

An acceleration is defined as the change of velocity in a unit of time. So with a constant acceleration, the velocity-over-time graph increases linearly. The kinetic energy of a body is simply proportional to the area under the velocity-over-time graph. (Energy = Work done = Force x Distance, and Distance is the area under the velocity-over-time graph) Thus the kinetic-energy-over-time graph increase is parabolic. This is well established Classical Physics. It obeys conservation of energy.

Of course, once Relativity is brought into the calculations, the faster the object travels the heavier it gets, and so more and more energy needs to be added to achieve the same acceleration. This increase is exponential and the speed of light can never actually be reached. To do so would require an infinite amount of energy.

Declan Traill

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>This is what I could rescue from my original rebuttal. When answering rebuttals, please post a new comment, instead of interleaving and indenting in the middle of the previous rebuttal. Thanks<

That's not a debunking theory, it is an energy and acceleration consideration. It fails to take into consideration the 2nd law of thermodynamics, it makes an unwarranted assumption that the acceleration of the device (and hence the force F= m *a) should be constant under constant power (the power required for constant acceleration is not explicitly discussed), and it fails to consider that in many processes like for example a collision against a wall momentum is conserved but kinetic energy is not. This same "debunking theory" could be applied to any flying vehicle: rockets are not possible because, to start from an initial condition at rest, it means that they must accelerate, but constant acceleration means an energy puzzle, therefore there cannot be any rocket. (It fails on the same philosophical grounds as Zeno's paradox https://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Paradoxes_of_motion that motion is not possible, this time by making the unwarranted assumption that the EM Drive will have constant acceleration at constant power.)

The issue of energy conservation has its own section in this wiki, and it has been better addressed by @frobnicat.

Perhaps the writer was unaware of the section titled "http://emdrive.echothis.com/Generic_EM_Drive_Information", and that section should be better titled "Energy Conservation."


Added: the writer offers three equations as her "back of the envelope proof". The first equation is Newton's 2nd law. Her third equation is Newton's 2nd law inverted in terms of acceleration (so nothing new, it is exactly the same as her first equation). Inverting an equation is not a proof. The second equation is the elementary definition of kinetic energy for a one-degree of freedom lumped mass. Stating a definition of kinetic energy is not a proof.

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That's not a debunking theory, it is an energy and acceleration consideration. It fails to take into consideration the 2nd law of thermodynamics, it makes an unwarranted assumption that the acceleration of the device (and hence the force F= m *a) should be constant under constant power (the power required for constant acceleration is not explicitly discussed), and it fails to consider that in many processes like for example a collision against a wall momentum is conserved but kinetic energy is not.

 This is a back-of-the-envelope look at the claim.  It is not meant to be exhaustive, it does not require efficiencies, nor does it deny the existence of new physics, it is simply to show that they are *required* if no sources of experimental error are identified. 

This same "debunking theory" could be applied to any flying vehicle: rockets are not possible because, to start from an initial condition at rest, it means that they must accelerate, but constant acceleration means an energy puzzle, therefore there cannot be any rocket.

 No, a rocket loses mass.  It converts some form of energy (usually chemical) to kinetic energy and throws mass out the back.  There is no 'energy puzzle' with a rocket.   Let us for the purpose of our back-of-the-envelope discussion assume the existence of rockets.

(It fails on the same philosophical grounds as Zeno's paradox https://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Paradoxes_of_motion that motion is not possible.

 It has nothing to do with Zeno's paradox.   

This time by making the unwarranted assumption that the EM Drive will have constant acceleration at constant power.)

 It is true that that is my assumption.  But is it really unwarranted?  It was quoted in the early NASA paper as a thrust to power ratio of 5.3 micro-Newtons per watt.  However, if this is somehow frame dependent in contravention to general relativity, which I have also assumed, then they would have seen a variance as the device was pointed in different directions given the absolute movement of the galaxy, sun and the earth. No such variance was seen as far as I am aware and thus tends to discredit your hypothesis.  Nevertheless, if general relativity were to fall I think that would still constitute new physics.

The issue of energy conservation has its own section in this wiki, and it has been better addressed by @frobnicat.

Perhaps the writer was unaware of the section titled "http://emdrive.echothis.com/Generic_EM_Drive_Information", and that section should be better titled "Energy Conservation"

 I was unaware of that section and will happily contribute there if there is anything I can feel I can add.  Thank you.  I am not sure of the best way to format a rebuttal of a rebuttal so I have interleaved and indented as above.  

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I'm not sure who wrote it as they were anonymous, all I did was format it. I agree it would be better suited to http://emdrive.echothis.com/Generic_EM_Drive_Information, along with your rebuttal.

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ADMINISTRATOR: Can you please change the section where the energy discussion takes place from "Generic Information" to "Energy Conservation" or something like that ?

There are many people bothered by the energy puzzle with the EM Drive, and conservation of Energy should have its own page instead of being buried under "Generic Information"

Actually I suggest the creation of two separate pages for people to write about these issues that they care so much about:

1) CONSERVATION OF ENERGY

2) CONSERVATION OF MOMENTUM

--- Done. I created these 2 new pages (Momentum is blank for now) and moved the above discussion to http://emdrive.echothis.com/Talk:Energy_Conservation - feel free to move the discussion to the main page. I don't know of the best format for the rebuttals either. - Rolf (aka admin - I've got to figure out how to change my username :) )