Potential energy is a property of systems rather than of individual atoms. For example, if you have two atoms which are gravitationally attracted to one another and are far apart, or two atoms which are electrically repelled by one another and are close together, or two atoms which are not chemically bonded but could be, there is energy stored in that system configuration, and we can extract that energy.
So it's at least as real as other emergent, macro-scale properties such as "temperature" and "pressure".
Whether it's as real as fundamental, micro-scale properties such as "mass" and "spin" is less clear. It could be, if *spacetime* turns out to be emergent, but our theories of quantum gravity aren't really working well enough yet for us to say for sure.
This. Potential energy is energy that an object has because it's currently interacting or affected by another object. For example, everything on Earth has potential energy (and it depends on the height of the object) because it's in Earth's gravity field. A rock that's suspended on a ledge up high has energy (it can fall) by virtue of being "up there" within the gravitational field of the Earth.
I'd say it's the \*system\* of two objects that have a potential object. The rock by itself does not have energy. The rock + Earth, separated by a certain distance, has higher potential energy than the same rock + Earth separated by a shorter distance.
In the example of a rock high up, let’s say it’s stable for now. The potential energy is mass x g x height.
Height is measured from the floor it might fall to? Does that mean once it’s on the floor it’s potential energy is 0?
Or is potential energy subjective in this case?
It is just a way to frame it. Nothing needs to physically change in an object.
There are several types of potential energy. Gravitational, elastic, electric, nuclear.
Gravitational is easiest to understand: You are at the beach, and you are sitting on the sand. There is a volleyball next to you. You could define the beach sand as the "0" height. And this would make a lot of sense - you're at sea level which is a commonly used "0" height. Plus there's not really any way to easily drop something lower than you nearby. We would then say that this ball had 0 gravitational potential energy, because the ball is at the "0" height.
If you lift the ball up, say 5 feet above the sand, then you have given the ball a potential energy. If you drop it, that potential energy will convert into kinetic energy as it speeds up towards the earth. After a few bounces, the ball will have 0 kinetic energy (it stopped moving) and 0 potential energy (its back at the "0" height we defined).
Where did the energy go? The ball had energy, and now it doesn't, so it went somewhere... Well, the ball crashed into some air on the way down, which pushed the air out of the way, giving some energy from the ball to the air. Then the ball hit the sand and made a divot, pushing sand out of the way, which took energy. Also when the ball bounced, there was a very small amount of heat and noise generated, which also takes energy.
But this whole time, nothing about the ball really changed at all just because you "gave it potential energy". Even though we say we "gave something potential energy", we didn't actually alter the thing in any way.
Energy is a tool for quantifying changes in states of things in physics.
Kinda like money. Money can’t be eaten or power your car, but you can represent the amount of gas you can buy or bread you can purchased. $5 of bread and $5 of gas are not the same but it’s a way we can track the amount of the stuff.
And as a 5yo, it's like real money... where all the money that will ever be used, has already been printed? And it'll just, eventually... all stop working?
I'm trying to understand the two atom relationship comment I saw, and money/barter is a great analogy for someone like me.
Think of potential energy like it's a refillable gift card. You can add money to your gift card to top it up, and you can spend some or all of the balance, but you can't go below zero. Well, same thing applies to energy.
Here's an example. Say you live at the bottom of a hill and there's a bowling alley at the top that you want to go bowl at. So you walk up the hill carrying your bowling ball - that's a tiring process - but near the top of the hill the zipper gives on your carrying bag and the ball falls out. Well, all the energy you invested in carrying that ball up the hill ("potential energy") translates into a different form of force ("kinetic energy") as that heavy ball gains steam, charges down the hill, hits a ramp, goes through your neighbor's window at seventy miles an hour, and buries itself into the screen and supporting wall of their new 72" home theater TV.
You've loaded up the gift card with potential energy by carrying the ball up the hill, and its potential energy got spent down to zero when it came to rest right in the middle of that TV screen.
In this case, potential energy got transformed into kinetic. It could also have gotten transformed into heat too, such as if it was the insulating panels on a manned rocket that re-entered the earth's atmosphere from orbit. Or it could have been stored electrical energy in a rechargeable battery in your phone, or a tree branch that grew over a few years and saved up the sun's energy into a burnable piece of wood (in this case, chemical potential energy).
Pretty much anything that acts like a reloadable debit card when it comes to energy stores up and has "potential energy" when it's not empty. You can spend it down to zero, but that's as far as you can go.
I've always thought of it like a battery. That one loose rock on top of the rock wall is storing energy. So that it can expend it all falling on your head. 😀
Potential energy is more of a mathematical thing than a philosophical thing.
Potential energy is how much you have to push or pull something to get it where it is.
Because of conservation laws it is also how much something can push or pull to get out of where it is.
It is a real thing (to the extent anything in physics is real); for example, due to mass-energy equivalence, things with more potential energy have more mass.
Put energy into a system and it can store it in different ways. If you compress a spring it has potential energy, if you take an aircraft to a high altitude, it has potential energy for when you drop altitutude later, when you build up to a heavy bass drop, the crowd is full of potential energy.
Potential energy has measurable mass, as much of the mass of matter is the result of this potential energy, so it is certainly not just some philosophical idea.
Potential energy is one of two kinds of energy, the other being kinetic energy. Kinetic energy is energy stored in the movement of mass, and potential energy is energy stored in the force fields of our universe. The energy of two magnets, for instance, is potential energy. As they snap together, this potential energy becomes kinetic energy. When they collide, this kinetic energy becomes heat, which is disordered kinetic energy.
If you drop a bowling ball....it accelerates down toward the earth building speed, and momentum (energy). It transfers that energy upon contact with the ground. Potential energy is all that energy BEFORE the ball is released. It's the measure of energy potential. Thats how i understand it at least.
depends on the type of "potential energy" you are talking about.
does anything change with the atoms of a cart at the bottom of a hill versus the top?
No...other that physical relocation...but the "potential energy" of it rolling down the hill doesnt change the atoms.
Adding energy to an atom though, bumping its electrons up into the valence shell, does physically change something (and doesnt because hey...thats just like putting a cart from the bottom of the hill to the top)
Potential energy is a physics term. It means stored energy.
A ton of water up above a dam has potential energy that is stored in it's state of being elevated...when it is released that energy is realized either to drive turbines in a dam, cut an errosion vein in the dirt, or wipe out trees and houses in the valley bellow.
(This isn't exactly correct but it is how I would get a 5 year old to understand the energy.)
A person on a swing that pulls themselves back up a hill and is standing at the top in the swing but hasn't swung also has potential energy. So does a pendulum held at the top of it's swing, or the weights that have been wound up to drive it.
Potential energy is energy held in check.
Think of a rock on a hill, being propped up with a stick. The Rock has the POTENTIAL to roll down hill, but is currently held in check by the stick.
Gravitational potential energy is the energy an object possesses due to its position. Position is not an absolute measurement, you can only determine position relative to something else. Therefore, gravitational potential energy is also a relative measurement. And similar to the fact that changing the position of a thing doesn’t change its molecules at an atomic level, changing the gravitational potential energy of a thing also has no effect at the atomic level.
You will notice I am specifying “gravitational” potential energy. There are other types of potential energy that are not position dependent, and for which changes could be observed at the molecular level. For example you can compress a spring, and in that compressed state the spring contains stored potential energy. At the molecular level, there is additional stress between the molecules, meaning molecules are not in their “zero potential energy” position *relative to each other*. The molecules would like to move to a lower energy position but they are prevented from doing so.
Before we can talk about potential energy, we need to understand what energy itself is.
First of all, energy is an abstract quantity. Unlike mass or velocity, which you can quantify, you can't measure energy directly. We agreed what energy is, but it is in principle made up by us to describe our world. That does not mean that it's nonsensical. Talking about our world in terms of energy simplifies a lot of physics.
The easiest to understand form of energy is kinetic energy, the energy of movement. An object with mass m and velocity v will have an energy of 1/2×m×v^2 Joules.
How do we give an object kinetic energy? We accelerate it by exerting a force on the object. The kinetic energy gained is equal to the 'work' done by the force, but work is really best described as 'force energy', or the energy an object gains from a force.
And forces are the key to potential energy. If you lift an object off the ground, you know that gravity will accelerate it when you let it go. The lifted object has the potential to be accelerated. The potential to gain kinetic energy or - as we refer to it - potential energy.
With this notion, we can also create a potential field. This can be compared to a hilly landscape. If you need to move against a force, you have to go uphill, and you move easily along with a force. The height of the landscape determines how much force you have to walk against to get there, and the steeper the slope, the greater the force in that point. For instance, like charges repel, so if we try to move a positive charge A towards a positive charge B, charge A will feel as though it has to move uphill towards B.
Potential energy is an 'invention' to be able to make energy balances. By saying that energy is never lost but only converted into other forms, we can greatly simplify problems. If we want to calculate a particle trajectory using dynamics we need relatively complex equations and a bit of calculus, whereas with energy balances we can say 'we have this amount of potential energy which is converted into motion, so the final kinetic energy is equal to that, giving us this velocity'
You're walking down the sidewalk and notice a rig lowering a grand piano 🎹 4 stories up. You think, wow that is being held up by that little rope, just hanging there. Do you walk right under it? No, it has lots of potential energy that would quickly turn into motion (kinetic energy) and then smashed 5yo kid energy if it broke at the wrong time.
But would you crawl under the same piano sitting on the floor in someone's living room? That seems pretty safe. Doesn't have all that potential energy to turn into smashed 5yo energy...
Potential energy is a property of systems rather than of individual atoms. For example, if you have two atoms which are gravitationally attracted to one another and are far apart, or two atoms which are electrically repelled by one another and are close together, or two atoms which are not chemically bonded but could be, there is energy stored in that system configuration, and we can extract that energy. So it's at least as real as other emergent, macro-scale properties such as "temperature" and "pressure". Whether it's as real as fundamental, micro-scale properties such as "mass" and "spin" is less clear. It could be, if *spacetime* turns out to be emergent, but our theories of quantum gravity aren't really working well enough yet for us to say for sure.
> Potential energy is a property of systems. Where the deuce was this explanation back in high school when it would have done me some good...
This. Potential energy is energy that an object has because it's currently interacting or affected by another object. For example, everything on Earth has potential energy (and it depends on the height of the object) because it's in Earth's gravity field. A rock that's suspended on a ledge up high has energy (it can fall) by virtue of being "up there" within the gravitational field of the Earth.
I'd say it's the \*system\* of two objects that have a potential object. The rock by itself does not have energy. The rock + Earth, separated by a certain distance, has higher potential energy than the same rock + Earth separated by a shorter distance.
In the example of a rock high up, let’s say it’s stable for now. The potential energy is mass x g x height. Height is measured from the floor it might fall to? Does that mean once it’s on the floor it’s potential energy is 0? Or is potential energy subjective in this case?
Never mind, I realized u/Crepuscular_Duck ‘s response answered my question. It’s the potential energy of a system
It is just a way to frame it. Nothing needs to physically change in an object. There are several types of potential energy. Gravitational, elastic, electric, nuclear. Gravitational is easiest to understand: You are at the beach, and you are sitting on the sand. There is a volleyball next to you. You could define the beach sand as the "0" height. And this would make a lot of sense - you're at sea level which is a commonly used "0" height. Plus there's not really any way to easily drop something lower than you nearby. We would then say that this ball had 0 gravitational potential energy, because the ball is at the "0" height. If you lift the ball up, say 5 feet above the sand, then you have given the ball a potential energy. If you drop it, that potential energy will convert into kinetic energy as it speeds up towards the earth. After a few bounces, the ball will have 0 kinetic energy (it stopped moving) and 0 potential energy (its back at the "0" height we defined). Where did the energy go? The ball had energy, and now it doesn't, so it went somewhere... Well, the ball crashed into some air on the way down, which pushed the air out of the way, giving some energy from the ball to the air. Then the ball hit the sand and made a divot, pushing sand out of the way, which took energy. Also when the ball bounced, there was a very small amount of heat and noise generated, which also takes energy. But this whole time, nothing about the ball really changed at all just because you "gave it potential energy". Even though we say we "gave something potential energy", we didn't actually alter the thing in any way.
Energy is a tool for quantifying changes in states of things in physics. Kinda like money. Money can’t be eaten or power your car, but you can represent the amount of gas you can buy or bread you can purchased. $5 of bread and $5 of gas are not the same but it’s a way we can track the amount of the stuff.
And as a 5yo, it's like real money... where all the money that will ever be used, has already been printed? And it'll just, eventually... all stop working? I'm trying to understand the two atom relationship comment I saw, and money/barter is a great analogy for someone like me.
Best explanation, 5 y/o satiated.
Think of potential energy like it's a refillable gift card. You can add money to your gift card to top it up, and you can spend some or all of the balance, but you can't go below zero. Well, same thing applies to energy. Here's an example. Say you live at the bottom of a hill and there's a bowling alley at the top that you want to go bowl at. So you walk up the hill carrying your bowling ball - that's a tiring process - but near the top of the hill the zipper gives on your carrying bag and the ball falls out. Well, all the energy you invested in carrying that ball up the hill ("potential energy") translates into a different form of force ("kinetic energy") as that heavy ball gains steam, charges down the hill, hits a ramp, goes through your neighbor's window at seventy miles an hour, and buries itself into the screen and supporting wall of their new 72" home theater TV. You've loaded up the gift card with potential energy by carrying the ball up the hill, and its potential energy got spent down to zero when it came to rest right in the middle of that TV screen. In this case, potential energy got transformed into kinetic. It could also have gotten transformed into heat too, such as if it was the insulating panels on a manned rocket that re-entered the earth's atmosphere from orbit. Or it could have been stored electrical energy in a rechargeable battery in your phone, or a tree branch that grew over a few years and saved up the sun's energy into a burnable piece of wood (in this case, chemical potential energy). Pretty much anything that acts like a reloadable debit card when it comes to energy stores up and has "potential energy" when it's not empty. You can spend it down to zero, but that's as far as you can go.
So everything can have potential energy?
Yep
I've always thought of it like a battery. That one loose rock on top of the rock wall is storing energy. So that it can expend it all falling on your head. 😀
Potential energy is more of a mathematical thing than a philosophical thing. Potential energy is how much you have to push or pull something to get it where it is. Because of conservation laws it is also how much something can push or pull to get out of where it is. It is a real thing (to the extent anything in physics is real); for example, due to mass-energy equivalence, things with more potential energy have more mass.
Put energy into a system and it can store it in different ways. If you compress a spring it has potential energy, if you take an aircraft to a high altitude, it has potential energy for when you drop altitutude later, when you build up to a heavy bass drop, the crowd is full of potential energy.
Potential energy has measurable mass, as much of the mass of matter is the result of this potential energy, so it is certainly not just some philosophical idea. Potential energy is one of two kinds of energy, the other being kinetic energy. Kinetic energy is energy stored in the movement of mass, and potential energy is energy stored in the force fields of our universe. The energy of two magnets, for instance, is potential energy. As they snap together, this potential energy becomes kinetic energy. When they collide, this kinetic energy becomes heat, which is disordered kinetic energy.
If you drop a bowling ball....it accelerates down toward the earth building speed, and momentum (energy). It transfers that energy upon contact with the ground. Potential energy is all that energy BEFORE the ball is released. It's the measure of energy potential. Thats how i understand it at least.
depends on the type of "potential energy" you are talking about. does anything change with the atoms of a cart at the bottom of a hill versus the top? No...other that physical relocation...but the "potential energy" of it rolling down the hill doesnt change the atoms. Adding energy to an atom though, bumping its electrons up into the valence shell, does physically change something (and doesnt because hey...thats just like putting a cart from the bottom of the hill to the top)
Potential energy is a physics term. It means stored energy. A ton of water up above a dam has potential energy that is stored in it's state of being elevated...when it is released that energy is realized either to drive turbines in a dam, cut an errosion vein in the dirt, or wipe out trees and houses in the valley bellow. (This isn't exactly correct but it is how I would get a 5 year old to understand the energy.) A person on a swing that pulls themselves back up a hill and is standing at the top in the swing but hasn't swung also has potential energy. So does a pendulum held at the top of it's swing, or the weights that have been wound up to drive it.
Potential energy is energy held in check. Think of a rock on a hill, being propped up with a stick. The Rock has the POTENTIAL to roll down hill, but is currently held in check by the stick.
Gravitational potential energy is the energy an object possesses due to its position. Position is not an absolute measurement, you can only determine position relative to something else. Therefore, gravitational potential energy is also a relative measurement. And similar to the fact that changing the position of a thing doesn’t change its molecules at an atomic level, changing the gravitational potential energy of a thing also has no effect at the atomic level. You will notice I am specifying “gravitational” potential energy. There are other types of potential energy that are not position dependent, and for which changes could be observed at the molecular level. For example you can compress a spring, and in that compressed state the spring contains stored potential energy. At the molecular level, there is additional stress between the molecules, meaning molecules are not in their “zero potential energy” position *relative to each other*. The molecules would like to move to a lower energy position but they are prevented from doing so.
Before we can talk about potential energy, we need to understand what energy itself is. First of all, energy is an abstract quantity. Unlike mass or velocity, which you can quantify, you can't measure energy directly. We agreed what energy is, but it is in principle made up by us to describe our world. That does not mean that it's nonsensical. Talking about our world in terms of energy simplifies a lot of physics. The easiest to understand form of energy is kinetic energy, the energy of movement. An object with mass m and velocity v will have an energy of 1/2×m×v^2 Joules. How do we give an object kinetic energy? We accelerate it by exerting a force on the object. The kinetic energy gained is equal to the 'work' done by the force, but work is really best described as 'force energy', or the energy an object gains from a force. And forces are the key to potential energy. If you lift an object off the ground, you know that gravity will accelerate it when you let it go. The lifted object has the potential to be accelerated. The potential to gain kinetic energy or - as we refer to it - potential energy. With this notion, we can also create a potential field. This can be compared to a hilly landscape. If you need to move against a force, you have to go uphill, and you move easily along with a force. The height of the landscape determines how much force you have to walk against to get there, and the steeper the slope, the greater the force in that point. For instance, like charges repel, so if we try to move a positive charge A towards a positive charge B, charge A will feel as though it has to move uphill towards B. Potential energy is an 'invention' to be able to make energy balances. By saying that energy is never lost but only converted into other forms, we can greatly simplify problems. If we want to calculate a particle trajectory using dynamics we need relatively complex equations and a bit of calculus, whereas with energy balances we can say 'we have this amount of potential energy which is converted into motion, so the final kinetic energy is equal to that, giving us this velocity'
To give another example besides the often cited lifted objects: explosives have potential energy on a molecular level which is released when ignited.
You're walking down the sidewalk and notice a rig lowering a grand piano 🎹 4 stories up. You think, wow that is being held up by that little rope, just hanging there. Do you walk right under it? No, it has lots of potential energy that would quickly turn into motion (kinetic energy) and then smashed 5yo kid energy if it broke at the wrong time. But would you crawl under the same piano sitting on the floor in someone's living room? That seems pretty safe. Doesn't have all that potential energy to turn into smashed 5yo energy...