Thread: Kinetic energy is not a motion energy store

Near 70 years ago at school I was taught that bodies at speed have kinetic energy. I learnt that if I threw a ball into the air I gave it kinetic energy, which diminished as it rose and which was totally lost at its peak to potential energy. The maths equating potential and kinetic energies worked but it didn’t make sense and it still doesn’t.

Not long ago assisting my Granddaughter with her studies I read in her text book “anything moving has energy in its kinetic energy store”. It also described a gravitational potential energy store as “anything that has mass and is in a gravitational field”. It seems that most scientists support this view. I have even seen it spoken of in a Faraday Lecture.
When bodies in space have relative motion which body has this motion energy store? When I am running do I really have more energy than when I am at rest and if I double my speed do I quadruple my motion energy?

A ball is less than 0.0001% particles in space and my hand is equally so. Both are energy stable structures that do not want to merge because there would be no energy advantage in them doing so. When I accelerate my hand upward photon energy interactions between my hand particles and the ball particles lead to particles being pushed closer together. We feel the photon pressures on our hand particles. The ball’s particles like their stable energy state and they react to the spring like photon pressures that are pushing their particles closer together by accelerating with the hand.

When the hand stops accelerating the ball quickly releases any compression energies as thermal photons . It returns to its former round shape and stable energy state and sets off upward at whatever speed had been achieved. There is no motion related kinetic energy store. The kinetic energy formula 1/2 mv² was derived as the energy involved in accelerating or decelerating an object. As I see it changes to a body’s state of rest or of uniform motion are how particle structures avoid taking on energies that they don’t want.

That is a substantially different view to the teaching that gives a body in motion a kinetic energy store. Can anyone tell me why we still regard kinetic energy as a motion energy store?

Originally Posted by auldbert

but it didn’t make sense and it still doesn’t.

Why not?

When bodies in space have relative motion which body has this motion energy store?

The one you're not observing from.

When I am running do I really have more energy than when I am at rest

More KE, yes.

There is no motion related kinetic energy store.

Wrong.

The kinetic energy formula 1/2 mv2 was derived as the energy involved in accelerating or decelerating an object.

So why is there no term for acceleration in that equation?

As I see it changes to a body’s state of rest or of uniform motion are how particle structures avoid taking on energies that they don’t want.

So you see it incorrectly. How does one ascertain how much energy a body does or does not want?

That is a substantially different view to the teaching that gives a body in motion a kinetic energy store.

Agreed. But what evidence do you have that you are right?

Can anyone tell me why we still regard kinetic energy as a motion energy store?

Because it works.

Thanks Dywyddyr for your reply and by the way I love your icon. Even particle physicists at the LHC see their accelerated protons as having on board kinetic energies so I am very much on my own but I welcome the opportunity to further argue my case.

Why kinetic energy didn’t make sense to me.

It didn’t make sense because I had no idea of what energy was, but who does understand it? Richard Feynman, for example said: ‘It is important to realize that in physics today, we have no knowledge of what energy is.’ He also said ‘For those who want some proof that physicists are human, the proof is in the idiocy of all the different units which they use for measuring energy.’

The one you’re not observing from has the kinetic energy.

So, if I jump on a bus and the bus accelerates to 30 mph, all of the objects moving with relative motion to that bus have added kinetic energy stores that disappear when the bus arrives at the next bus stop.

Is kinetic energy acceleration related?

There are many ways of delivering the ½ mv² but they all involve acceleration. Here’s mine

For a steady force delivering an acceleration a
Velocity change = acceleration x time v - u = a x t
Average velocity = distance/time (v + u)/2 = s/t
Multiplying the two sides of these equations gives us (v –u)(v + u)/2 = a x t x s/t = a x s

Multiplying both sides by the accelerated mass m we get m x a x s = m(v² – u²)/2
As m x a is force and force x distance is energy Energy = m(v² – u²)/2

If we now take that starting velocity u to be zero Energy = 1/2mv²

But is this kinetic energy or work done? (both in Joules). Science confuses us by having it as the formula for both. Work done is the vector quantity that delivers the force and its directional motion whilst kinetic energy is the scalar energy store that is depleted doing that work.

Clearly science places this energy store on the moving body but this gives us problems? Moving a car from rest to 30 mph gives us an energy store related to that 30 mph. If that car collides with a 70 mph truck the energy store depletion is 100 mph related.

I say that when particle structures engage at relative speeds it is their photon energy exchanges that provide the decelerating and accelerating force. Kinetic energy is a vector quantity and there is no need of the work done quantity or of the “on board” energy store.

How do particle structures decide what energy they want and don’t want?

Nuclear changes, chemical changes and changes of state are all particle initiated. Particle structures only make such changes when it is in their interest to do so. Given the opportunity (as with an environmental change) they will choose to become more stable, more efficient energy processing states. If we are involved it is only to provide the conditions under which they will choose to make change.

When engaging structures can find no benefit in combining they both want to retain their stable energy states. Motion is a way of avoiding undesirable energy change. If something is putting pressure on you, you instinctively move away because your particles don’t want an excess of photon delivered energy pressure. Increasing, force delivering photon interactions between structures are related to their masses and speed of approach.

Evidence to support my view.

If I push a car interacting photon energies act between me and the car. Those photon kinetic energies add to its mass energy (Einstein 1905 paper), pushing, in a cascading fashion, its particles closer together. The car is a stable structure. It doesn’t want its energy changed. If it can it will move away and dissipate that added energy into space. If it can’t move it will wait until I have stopped pushing it and then dissipate those energies into space. Similarly when a rocket is fired on a launch pad unwanted photon energies add to the rockets mass which is why it wants away.

Things are different in the Large Hadron Collider. The light speed photons of the magnetic field are directed at the protons they want to accelerate but no way can we ensure that all of those energies act on the protons. However the idea that those protons were taking on all of the force delivering energies as a store prevailed and applying ½ mv² to those stored energies delivered speeds well in excess of light speed so E = ½ mv² had to be wrong at high speeds and was duly modified.

The protons don’t want those energies that are flattening them and giving them added mass energy. The protons are fleeing for their lives from those light speed photons. At near light speed they get some respite. If they could go at over light speed they would return to being normal protons. But instead we collide these abnormal energy photons with other abnormal energy photons and the interacting photon pressures between them are sufficient to break them.

If I haven’t convinced you that kinetic energy is interacting energy and not an energy store I hope I have at least got you thinking about such things.

Originally Posted by auldbert

Why kinetic energy didn’t make sense to me.
It didn’t make sense because I had no idea of what energy was, but who does understand it? Richard Feynman, for example said: ‘It is important to realize that in physics today, we have no knowledge of what energy is.’

Just because we don't know what it is doesn't prevent us from quantifying it.

He also said ‘For those who want some proof that physicists are human, the proof is in the idiocy of all the different units which they use for measuring energy.’

Entirely beside the point. We can measure the height of a human in multiple different units.

The one you’re not observing from has the kinetic energy.
So, if I jump on a bus and the bus accelerates to 30 mph, all of the objects moving with relative motion to that bus have added kinetic energy stores that disappear when the bus arrives at the next bus stop.

Correct.

Is kinetic energy acceleration related?
... elision ...
If we now take that starting velocity u to be zero Energy = 1/2mv²

Utterly irrelevant.
1/2mv² uses the instantaneous velocity - it doesn't consider acceleration at all.

Clearly science places this energy store on the moving body but this gives us problems? Moving a car from rest to 30 mph gives us an energy store related to that 30 mph. If that car collides with a 70 mph truck the energy store depletion is 100 mph related.

I don't see what the problem is here.

I say that when particle structures engage at relative speeds it is their photon energy exchanges that provide the decelerating and accelerating force.

You say this. But what's the EVIDENCE?

Evidence to support my view.
If I push a car interacting photon energies act between me and the car. Those photon kinetic energies add to its mass energy (Einstein 1905 paper), pushing, in a cascading fashion, its particles closer together. The car is a stable structure. It doesn’t want its energy changed. If it can it will move away and dissipate that added energy into space. If it can’t move it will wait until I have stopped pushing it and then dissipate those energies into space. Similarly when a rocket is fired on a launch pad unwanted photon energies add to the rockets mass which is why it wants away.

Things are different in the Large Hadron Collider. The light speed photons of the magnetic field are directed at the protons they want to accelerate but no way can we ensure that all of those energies act on the protons. However the idea that those protons were taking on all of the force delivering energies as a store prevailed and applying ½ mv² to those stored energies delivered speeds well in excess of light speed so E = ½ mv² had to be wrong at high speeds and was duly modified.

The protons don’t want those energies that are flattening them and giving them added mass energy. The protons are fleeing for their lives from those light speed photons. At near light speed they get some respite. If they could go at over light speed they would return to being normal protons. But instead we collide these abnormal energy photons with other abnormal energy photons and the interacting photon pressures between them are sufficient to break them.

None of this is EVIDENCE, it's claims with no support.

Once again Dywyddyr, thanks for your reply and my kindest regards for allowing me to express my views on this topic.

I agree I have no evidence but there is equally no evidence that supports the view that bodies in motion have an energy store. Many historical ideas like those of vis viva and many experiments as with Rumford’s boring of canons led to the kinetic energy formula ½ mv², but none of them establishes this energy as a motion energy store that is carried by a freely moving object and indeed Einstein’s first postulate sees no difference between a moving body and a body at rest.

I think the major difference between us is that you view energy as quantitative, the result of a calculation, a measure that is different for different observers and different when considering changed relative motions. That being the case I think store is a misleading word because it leads to the thinking that there is “on-board” energy related to the motion. This quantitative view is, I suppose, why we talk of photons as carrying energy and not as energy. I don’t see energy as a substance but I do see photons as energy pulses delivering forces between particles and responsible for their motions and I do see particles as having photon desires.

The ½ mv² calculation works but like many other calculations it doesn’t contribute to our understanding of what is really going on. For example, a formula leads us to say that temperature causes energy to move from a hot to a cold state. But temperature is just a measure of the agitated state of photon interactions. Temperature is not the cause of a conduction energy flow. Energy decisions made by particles are responsible for any redistribution of energy.
.
Mathematically kinetic energy is involved in the equation mc² = m₀c² + kinetic energy where m is relativistic mass, m₀ is rest mass and c is of course the speed of light. Many argue that relativistic mass is outdated but others insist on its use. Others say shut up and calculate because either way the calculations work. I have a simple solution, stop thinking of kinetic energy as a motion energy store.

You are well supported in your quantitative viewpoint by the IOP (Institute of Physics UK) who having concerns about the substance view of energy taught, have and are introducing changes that give a more quantitative view of energy. They want explanations of processes to limit energy references to that of stores but only at the start and end of the process and which in later education can be supported by calculations.

The stores they suggest are gravitational, elastic, kinetic, thermal, electromagnetic, chemical, nuclear and that of vibrations. As regards kinetic energy they recognise that some are not comfortable thinking of a moving object as storing energy and recommend that kinetic energy is only referred to in circumstances where it is necessary to do so, as for example in discussing the braking of a car.

I welcome the explanation of processes but the quantitative approach that is intent on leading to calculations that most children will never, in their post educational lives, have to use again seems nonsensical. It would be much better to talk about what all those energy stores have in common and what the quantum and classical worlds of physics have in common with all the other branches of science. Maybe chemistry could take the lead on this one as physics seems to have no way of simply explaining energy at the particle level.

Energy is the basis of everything in our universe. I see it as a living, proactive thing, there at the particle level and in the photon energies they exchange. If we want to understand everything we need to understand the nature of energy at that level.

Originally Posted by auldbert

That being the case I think store is a misleading word because it leads to the thinking that there is “on-board” energy related to the motion.

Except the evidence leads to this conclusion.

Many argue that relativistic mass is outdated but others insist on its use.

The argument was that the term (not the concept) is outdated. That view is falling out of favour.

You are well supported in your quantitative viewpoint by the IOP (Institute of Physics UK) who having concerns about the substance view of energy taught, have and are introducing changes that give a more quantitative view of energy.

Link, please, to the latter claim.

As regards kinetic energy they recognise that some are not comfortable thinking of a moving object as storing energy and recommend that kinetic energy is only referred to in circumstances where it is necessary to do so, as for example in discussing the braking of a car.

Really? Where did you get this idea, since a quick check of the IoP website has many references to KE, e.g "moving pencil uses kinetic energy" and here.

I see it as a living, proactive thing, there at the particle level and in the photon energies they exchange. If we want to understand everything we need to understand the nature of energy at that level.

Something else you no evidence for, presumably.

As a member of the Institute of Physics, even if your claim is correct(*) and they are moving to that interpretation of kinetic energy as a teaching method, it still in no way validates your crackpot woo.

* Which has yet to be shown.

auldbert
That being the case I think store is a misleading word because it leads to the thinking that there is “on-board” energy related to the motion.

Dywyddyr
Except the evidence leads to this conclusion.


You are critical of my not providing evidence, so what evidence leads to the conclusion that a body in motion has an “on board” energy store?

You yourself have told me that kinetic energy is relative and that every object being passed by a bus will have kinetic energy relative to an observer on that bus. Now you are telling me that evidence has concluded that every one of those objects will have an on-board energy store for as long as the bus has that relative motion and the argument For the observer on the bus the only thing not having a motion energy store, is the bus. I can accept 1/2mv² as an energy measure but I would be embarrassed trying to explain the seemingly crazy world of kinetic energy stores.

How much easier to accept that elastic compression energies do work of 1/2mv² on an object giving it motion (without transferring energy to it) and that elastic compression energies or gravitational desires will similarly do work on that object of ½ mv² by opposing its motion and stopping it.

Having said that it is clear that I am not going to convince you and you are not going to convince me and, as this debate is between just the two of us, I will be interested in any reply you make but will not withdraw from it. Thanks again Dywyddyr for your input.

The link requested is https://spark.iop.org/collections/energy-new-curriculum

Originally Posted by auldbert

auldbert
That being the case I think store is a misleading word because it leads to the thinking that there is “on-board” energy related to the motion.

Dywyddyr
Except the evidence leads to this conclusion.


You are critical of my not providing evidence, so what evidence leads to the conclusion that a body in motion has an “on board” energy store?

You yourself have told me that kinetic energy is relative and that every object being passed by a bus will have kinetic energy relative to an observer on that bus. Now you are telling me that evidence has concluded that every one of those objects will have an on-board energy store for as long as the bus has that relative motion and the argument For the observer on the bus the only thing not having a motion energy store, is the bus. I can accept 1/2mv² as an energy measure but I would be embarrassed trying to explain the seemingly crazy world of kinetic energy stores.

How much easier to accept that elastic compression energies do work of 1/2mv² on an object giving it motion (without transferring energy to it) and that elastic compression energies or gravitational desires will similarly do work on that object of ½ mv² by opposing its motion and stopping it.

Having said that it is clear that I am not going to convince you and you are not going to convince me and, as this debate is between just the two of us, I will be interested in any reply you make but will not withdraw from it. Thanks again Dywyddyr for your input.

The link requested is https://spark.iop.org/collections/energy-new-curriculum

It is only you that is going on and on about "an on-board energy store". No one else has signed up to that idea, whatever it may mean. It sounds childish and misleading.

We all agree you are right that the kinetic energy depends on the chosen frame of reference. That is hardly news and in no way justifies the unevidenced leap you seem to be making by dragging in photons, of all things.

Energy is book-keeping, in much the same way as momentum is. It is not "stuff".

Originally Posted by exchemist

It is not "stuff".

Good answer. It gets to the heart of the matter. I've been trying to think of a reply to this thread, but nothing I could think of answers the question quite like "energy is not stuff". And if conservation becomes a problem, you can throw in a Noether.

Originally Posted by auldbert

The link requested is https://spark.iop.org/collections/energy-new-curriculum

Ah. So when you wrote "OP (Institute of Physics UK) who having concerns" you meant "with regard to teaching 12-year-olds, and only under certain circumstances".

Originally Posted by exchemist

Originally Posted by auldbert

You are critical of my not providing evidence, so what evidence leads to the conclusion that a body in motion has an “on board”…

It is only you that is going on and on about "an on-board energy store". No one else has signed up to that idea, whatever it may mean. It sounds childish and misleading.

We all agree you are right that the kinetic energy depends on the chosen frame of reference. That is hardly news and in no way justifies the unevidenced leap you seem to be making by dragging in photons, of all things.

Energy is book-keeping, in much the same way as momentum is. It is not "stuff".

Exchemist has it exactly right: There is no “energy particle” that stores the energy, auldbert. That the energy is frame-dependent is an important clue as to the non-existence of an energy storehouse. As exchemist says, keeping track of energy is an accounting exercise. Throwing photons at the accounting problem only distracts; I don’t see how it elucidates.

Your entire approach to understanding is flawed. You begin with “I don’t understand what the textbooks say”, and jump to “Therefore, the textbooks are wrong.” There is another possibility, which is understandably unpalatable to you, but which requires serious consideration if one wishes to be be complete: That is, you could be wrong. Certainly, you have an idiosyncratic idea about what science has to say about the subject. (By “idiosyncratic”, I do mean “wrong”.)

Physics Wikipedia

"Physics is the natural science that studies matter, its fundamental constituents, its motion and behaviour through space and time, and the related entities of energy and force. "

Entity

"A thing with distinct and independent existence "

Can anyone tell me what is at the heart of all motions and behaviours through space and time if it is not energy.

Originally Posted by auldbert

Physics Wikipedia

"Physics is the natural science that studies matter, its fundamental constituents, its motion and behaviour through space and time, and the related entities of energy and force. "

Entity

"A thing with distinct and independent existence "

Can anyone tell me what is at the heart of all motions and behaviours through space and time if it is not energy.

That just goes to show there can be some poor draftsmanship in Wikipaedia from time to time.

One might think that if you are really interested in getting at the nature of what energy is, you would look up "Energy" in Wikipaedia, rather than, for some reason, "Physics". If you had done that, you would see it says that energy is a property of a body or system. That's exactly right. As I said in my previous post, energy is like momentum in that it is a conserved quantity that is a property of a system.

Nobody is under the illusion that momentum is a thing in its own right, with an existence independent of a system, any more than they think velocity can exist on its own. But for some reason people do have this wrong idea about energy. (I blame Star Trek, with its nonsense about "pure energy", "energy fields" and so on. It's become a thing in popular culture, but it's just wrong.)

As to what is "at the heart of all motions and behaviours in space and time" that is simply not a question with any meaning in physics. Why do you think there should be any one thing that is "at heart of " everything in this way? And what does "at the heart of" mean, in the context of physics? It is true that in principle one can try to determine the energy of any body or system. But one can do that for mass in just the same way, or for momentum. Energy is useful for analysing systems and so is momentum.

But all this is getting rather a long way from this "on-board energy store" of yours. I think we can all agree that that is not a helpful way of thinking about kinetic energy, it is not what physics says, and you can safely dump it. Which I imagine should make you happy.

(Unless of course this whole kinetic energy thing is just a Trojan Horse for introducing some personal crankery................... )