Is potential energy real or fictious..?

A.T.

Would you rather pay money for a quantity that is not conserved, and can be created out of nothing? That would be stupid. In theory the value of your money should also be conserved, but this is unfortunately not a law of physics.

sophiecentaur

Haha. But the laws of money are not conservative. It changes value to suit the economic climate. I would just hope the failure of conservation would be in my favour. But then, I'm not a banker.

Nano-Passion

I'm not convinced, I'm in the philosophy that things should ultimately make sense or else we don't understand it. If we just invented a few concepts to make the math work than it implies that we have missing holes in our understanding. I think a good role model is the equation for rest energy "mc^2." It seems that it takes us a bit closer to the fundamental.

Kinetic energy seems more real than potential energy. Potential energy just says particle A has so and so potential.

Kinetic energy tells me that I can deal this much damage with a bullet with mass m and velocity v.


You seem to take the "real" argument a bit too far. Electrons are more real than potential energy. One is tangible and we use it in our daily lives even if it isn't what we "really" think it is, while the latter sounds like a bookkeeping device.

aditya23456

Nano-Passion
I guess ur right..Can physics hold without concept of potential energy.?I guess not..so we need to believe it irrespective of it being real or fictious

Nano-Passion

It would have helped if it was explicitly stated. I've spent many hours grappling with the subject of potential energy. I'm the type of person that has to know a "why" for everything, so the superficiality of introductory physics texts drove me crazy.

Drakkith

Just because it doesn't make sense to you doesn't mean we don't understand it. Energy and potential energy are "made up" in the same way that mass or charge is made up. All are simply properties of something that we have defined a certain way.

Kinetic energy just says particle A can do such and such amount of work.

And potential energy lets you state how much energy something can acquire in the first place.

Neither is more real than the other unless you personally define one to be. And yes, you do use potential energy in your everyday life even if you don't realize it. Something as simple as knowing that riding a bicycle downhill will result in a very high speed unless you ride the brakes is a direct result of you knowing what potential energy is. Not in a scientific way, but in a functional way. The concept of potential energy is very real. It is simply different than an electron.

russ_watters

Well of course - you don't understand it, so it doesn't make sense to you. Just don't say "we" because there are plenty of us who do understand it. Welcome to physics. I'm sorry it isn't satisfying to you, but that's all [!] physics is.
Whatever problem you have with potential energy surely also exists for kinetic. I'm guessing your problem with potential energy is its frame dependence -- the same also exists for kinetic energy. The damage a bullet can do is not a singular quantity: it depends on what the bullet is being measured against. So as I said in your other thread: potential energy is exactly as "real" as kinetic. This is why this is a just plain bad question. The word "real" is poorly defined and really isn't useful here regardless of what it means. If you mean that to be real, it has to be an object, then information of any kind is not real, whether it is kinetic energy, potential energy or War and Peace. But this definition has no real value - calling it "real" or "not real" doesn't change its usefulness in physics, so it is just a bad question to ask. That's why you've been having so much trouble learning physics for so long on PF. You're asking meaningless questions, looking for existential meanings behind concepts in physics that just don't exist and ignoring the actual meanings of the concepts. This "real" or "not real" thing you are into on energy is not useful. Getting an answer that satisfies you will not in any way help you understand what energy is and in fact is acting as a substitute for learning what it actually is.

Nano-Passion

I don't agree with the philosophical premise that mass and charge are just as made up as a more abstract concept as potential energy. It is a bit relative, but mass and charge has direct affects to our daily lives in comparison to potential energy.

You can derive how much energy something can have through other means?

That is easily explained by saying that there is a constant acceleration down that is usually counteracted by the normal force, and once you are on a slope, there is less normal force to counteract the gravitational acceleration.

Nano-Passion

I understand it potential energy. It isn't that complicated. What is complicated is how it is talked about so often like its something of substance.

I was speaking in the casual sense not the literal sense.

It is useful for calculation but it is just as equally useless by not being a fundamental aspect of nature. There might be an alternative formalism to account for the conservation of energy.

russ_watters

Yes, that's fine. Physicists decided that that needed a name so they wouldn't have to type it all out every time they wanted to refer to it! That's how concepts in physics get names. They also noticed that that could calculated/quantified, so they use it in equations. I don't know what you mean or how this relates to your previous claim that "we" don't understand it. Again, this all seems pretty meaningless. I'm sorry, but that is just psuedophilosophical babbling. There is no such idea in science as "a fundamental aspect of nature", but even if there was, both kinetic and potential energy would rank the same on whatever scale you would use to measure the concepts.

Please be clearer: what exactly is it about potential energy that you don't like and how does kinetic energy differ? If it looks like a duck and quacks like a duck, you can call it a chicken if you want, but it is still a duck.

Nano-Passion

That is perfectly fine, but then it isn't real in the sense that some of the other concepts in physics are, its bookkeeping.

I said the previous statement on the assumption that potential energy was supposed to be a type of energy that affects the system's behavior, but now I see that not everyone follows that paradigm.

Some things are more fundamental than others. This has been the case ever since we have looked for equations that describe the very small and ever since the search for unification.

I'm not sure why it is noted that kinetic and potential energy are on the same scale.

The kinetic energy "of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity.

Potential energy "is the energy of a body or a system due to the position of the body or the arrangement of the particles of the system"

Kinetic energy is more tangible in the sense that we can use it to describe a lot of everyday phenomena such as the energy imparted on a ball by a bat swing. Potential energy seems like an accountant's tool to make sure all the toys in the box and out count up to X.

See comment above.

sophiecentaur

and many other quotes.

You are being very selective in your appreciation of Science. You base the above statement on a very narrow appreciation of the three example quantities. How can you be any more 'aware' of the presence of a mass or a charge other than by how they are reacting with you or something else? You drop a mass on your foot but its effect (how painful it gets) depends entirely upon its gravitational potential energy where you let it go. On Earth, it might break your toe but on the Moon it may just bounce off your shoe.

You are trying to impose a very personal view on all of this. Moreover, the further this thread goes, the more entrenched you seem to be getting. If you go away and think about this, rather than bouncing back with more and more arguments, trying to justify your view, then you may start to realise the advantage of thinking the way 'the rest of us' are thinking. When you do come to that conclusion, don't think of it as having been proved wrong. Just feel and enjoy the enlightenment. None of this is 'real'; it's just ways of thinking about things which allow us to make good predictions.

A.T.

"Making sense" and "understanding" are rather vague subjective terms and quite irrelevant to the goal of physics: making quantitative predictions. The concepts allow us to do this. Whether the concepts are intuitive to some person is very individual.
The original question was whether potential energy is somehow "more made up to ensure CoE" than other forms of energy. It's not. All the formulas to calculate various forms of energy are designed to ensure of CoE. Without CoE the concept of energy would be useless.

I would agree that subjectively, to most humans, the concept of energy as such is more abstract than say length, which humans can perceive more directly. Energy is more general and can be computed for apparently unrelated phenomena, which makes it hard to grasp it intuitively.

Michio Cuckoo

My god you people keep on arguing on what is real or not, even making me confused when I wasn't before.

Look, energy is force * distance. When you are repelled by an object, it exerts a force on you. Your kinetic energy is converted to potential energy, which determines how close you get to the object before stopping.

For god's sake.

sophiecentaur

Absolutely. √-1 makes very little sense to most people at first but it soon becomes meat and drink to those of us who have got over the initial "doesn't seem right" reaction. Some of the most abstract concepts get to feel at least as concrete as length and force when we use them regularly.

It's not unlike the taste of beer - which nearly all kids will gag at but most of us blokes find most acceptable.

sophiecentaur

Deepest sympathy.
We do a lot of angels on pinheads here.

The problem is that your approach may be a bit too simplistic if you want to progress to higher levels of this game. For instance, your definition of Energy is usually regarded as the definition of Work.

DrewD

All of physics is book keeping. What is a force except a number that is used to describe a change in momentum. It may seem more real because you can see something move. If you define that to be real, then you are correct.

Every physical system can be described in a formalism that uses only energy and not force. Very little modern physics considers forces at all. Instead, the formalism of Hamiltonian Mechanics is often used (I have to admit that a friend recently published a paper that heavily relied on forces for her analysis) which is based on kinetic and potential energy. Since the Newtonian and Hamiltonian Mechanics can both equally well describe the world without reference to the other, it seems to me that their basic components must be equally real.

Also, look up Aharonov-Bohm effect. It is certainly not the same thing, but since the relationship of force to force field is similar to energy to potential field it might help convince you. In short, this effect shows that the electromagnetic potential field can have measurable effects on particles where there is no electric field. Weird, yes. Also very real.

What level of physics have you studied? I expect that when you get to an upper level Mechanics course and QM, you will be better convinced that potential energy and forces are on the same level. As to using the word "real", leave it to the philosophy majors. They need something to do.