(July 23, 2019 at 9:45 am)comet Wrote:

(July 23, 2019 at 9:10 am)polymath257 Wrote: No, you misunderstood. Energy is NOT a vector. It is a *component of* a vector. More specifically, it is the time component of the energy-momentum 4-vector. So, in that sense, it has *exactly* the same 'reality as momentum. In other words, it is a *property* of the particles involved.

The PE and KE are not 'components in the vector sense. They are scalars that add up to be the total energy. But, you are working classically, and classical physics is ultimately wrong. When you get to relativistic physics, energy is one component of a four dimensional vector associated with the particle. And, in fact, the energy-momentum vector for a particle always has a (relativistic) length associated with the rest mass of the particle. That is where the equation E^2 = m^2 c^4 +p^2 c^2 comes from (the correct version of E=mc^2 to apply to moving and/or massless particles).

energy is a property that is used. as in "how much energy does it have?"   I think I get that. 

what type of energy is the time component of energy-momentum 4-vector?   what are its parts?

The energy in the energy-momentum 4-vector is the kinetic energy. The other three components of the 4-vector are the usual three components of the momentum.

Potential energy is, ultimately, the kinetic energy of the force carrying particles.  So *all* energy is ultimately kinetic energy.

(July 23, 2019 at 10:10 am)polymath257 Wrote:

(July 23, 2019 at 9:45 am)comet Wrote: energy is a property that is used. as in "how much energy does it have?"   I think I get that. 

what type of energy is the time component of energy-momentum 4-vector?   what are its parts?

The energy in the energy-momentum 4-vector is the kinetic energy. The other three components of the 4-vector are the usual three components of the momentum.

Potential energy is, ultimately, the kinetic energy of the force carrying particles.  So *all* energy is ultimately kinetic energy.

You also mentioned "energy is the Time component of ..." , whats that mean? energy is the time component?

(July 23, 2019 at 12:44 pm)comet Wrote:

(July 23, 2019 at 10:10 am)polymath257 Wrote: The energy in the energy-momentum 4-vector is the kinetic energy. The other three components of the 4-vector are the usual three components of the momentum.

Potential energy is, ultimately, the kinetic energy of the force carrying particles.  So *all* energy is ultimately kinetic energy.

You also mentioned "energy is the Time component of ..." , whats that mean? energy is the time component?

A vector has components. So, for example, a vector in two dimensions has an x-component and a y-component. A vector in three dimensions has three components: x,y, and z. A vector in four dimensions has four components: x,y,z, and t.

So, in the energy-momentum 4-vector, the x,y, and z components are the amounts of momentum in the x,y, and z directions. The t component is the energy.

Now, truthfully, if you didn't know what a vector is, you don't have even enough *classical* physics to have a *basic* knowledge of physics, and thereby even a basic understanding of energy. And to have a *modern* view requires a LOT more than just some knowledge of vector calculus.

(July 23, 2019 at 1:34 pm)polymath257 Wrote:

(July 23, 2019 at 12:44 pm)comet Wrote: You also mentioned "energy is the Time component of ..." , whats that mean? energy is the time component?

A vector has components. So, for example, a vector in two dimensions has an x-component and a y-component. A vector in three dimensions has three components: x,y, and z. A vector in four dimensions has four components: x,y,z, and t.

So, in the energy-momentum 4-vector, the x,y, and z components are the amounts of momentum in the x,y, and z directions. The t component is the energy.

Now, truthfully, if you didn't know what a vector is, you don't have even enough *classical* physics to have a *basic* knowledge of physics, and thereby even a basic understanding of energy. And to have a *modern* view requires a LOT more than just some knowledge of vector calculus.

I wish I had a physics teacher like you. Mine just throwed stuff in the blackboard and ask about it. I never did homework, but I liked to read my books in the train ride after school. I was so tangled with a simple derivative that when I looked outside I saw my stop going backwards. In the panic I jumped out of the accelerating train resulting in some moderate pain. That,s momentum, gravity and poor decision making in a single lesson.

(July 23, 2019 at 2:14 pm)LastPoet Wrote:

(July 23, 2019 at 1:34 pm)polymath257 Wrote: A vector has components. So, for example, a vector in two dimensions has an x-component and a y-component. A vector in three dimensions has three components: x,y, and z. A vector in four dimensions has four components: x,y,z, and t.

So, in the energy-momentum 4-vector, the x,y, and z components are the amounts of momentum in the x,y, and z directions. The t component is the energy.

Now, truthfully, if you didn't know what a vector is, you don't have even enough *classical* physics to have a *basic* knowledge of physics, and thereby even a basic understanding of energy. And to have a *modern* view requires a LOT more than just some knowledge of vector calculus.

I wish I had a physics teacher like you. Mine just throwed stuff in the blackboard and ask about it. I never did homework, but I liked to read my books in the train ride after school. I was so tangled with a simple derivative that when I looked outside I saw my stop going backwards. In the panic I jumped out of the accelerating train resulting in some moderate pain. That,s momentum, gravity and poor decision making in a single lesson.

Pity you weren't taught Einstein's theory of Acceleration Due To Panicking.  I'm sure most of us have got bumps and bruises for ignoring that one.

Boru

(July 23, 2019 at 2:30 pm)BrianSoddingBoru4 Wrote:

(July 23, 2019 at 2:14 pm)LastPoet Wrote: I wish I had a physics teacher like you. Mine just throwed stuff in the blackboard and ask about it. I never did homework, but I liked to read my books in the train ride after school. I was so tangled with a simple derivative that when I looked outside I saw my stop going backwards. In the panic I jumped out of the accelerating train resulting in some moderate pain. That,s momentum, gravity and poor decision making in a single lesson.

Pity you weren't taught Einstein's theory of Acceleration Due To Panicking.  I'm sure most of us have got bumps and bruises for ignoring that one.

Boru

After picking myself up, with an injury to the knee, I couldn't find my backpack with my books (while adrnalin is rushing, no pain), so I went to the station and asked the chief if any lost & found were found on the next station. They found it dangling on the train doorknob.

No injuries to trains or books.

(July 23, 2019 at 2:42 pm)LastPoet Wrote:

(July 23, 2019 at 2:30 pm)BrianSoddingBoru4 Wrote: Pity you weren't taught Einstein's theory of Acceleration Due To Panicking.  I'm sure most of us have got bumps and bruises for ignoring that one.

Boru

After picking myself up, with an injury to the knee, I couldn't find my backpack with my books (while adrnalin is rushing, no pain), so I went to the station and asked the chief if any lost & found were found on the next station. They found it dangling on the train doorknob.

No injuries to trains or books.

(bold mine)

When I was a kid, we had a school bus conductor, Mr. Curtis.  I'll never forget him as long as I live - he was hysterically funny and kind beyond belief.

He was always giving us sound advice, such as not to stand in front of the bus.  'If you do, you might get run down.  If you scratch my bus, I'll never forgive you.' And, 'If a dog bites you, bite him back.  I had to bite four dogs last week and they all died.'

Boru

(July 23, 2019 at 8:36 am)polymath257 Wrote:

(July 22, 2019 at 11:15 pm)Bucky Ball Wrote: But you can add just energy to the system. It is *something*.

No, you cannot just add energy to a system. To add energy, you have to apply a force. In other words, you have to interact with the system by some other system. Interactio between particles can, and does, change the dynamic properties of the particles involved. This includes energy and momentum, for example.

Energy is a property of the particles, not something that can be separated from them. Energy doesn't exist as a 'thing in itself', but solely as a property of such things: quantum particles.

---

So if one heats up a closed system, what is the "force", and what are the particles involved.

(July 23, 2019 at 3:35 pm)Bucky Ball Wrote:

(July 23, 2019 at 8:36 am)polymath257 Wrote: No, you cannot just add energy to a system. To add energy, you have to apply a force. In other words, you have to interact with the system by some other system. Interactio between particles can, and does, change the dynamic properties of the particles involved. This includes energy and momentum, for example.

Energy is a property of the particles, not something that can be separated from them. Energy doesn't exist as a 'thing in itself', but solely as a property of such things: quantum particles.

---

So if one heats up a closed system, what is the "force", and what are the particles involved.

If you are heating up a system, it is not closed.

But if, for example, you are heating up a pot of water, the molecules in the flame are colliding with the atoms/molecules pan, making them move faster (more kinetic energy--> hotter). Those, in turn, collide with the molecules of the water, making them move faster. The force is that of the collision between the molecules or atoms involved, which ultimately comes down to the electromagnetic force together with some quantum effects of the electrons, which are fermions and thereby don't like to be in the same location at the same time.

The flame is actually a chemical reaction, which again is ultimately a matter of the electromagnetic force, mostly between the electrons of the different atoms rearranging in the reaction.

(July 23, 2019 at 2:30 pm)BrianSoddingBoru4 Wrote:

(July 23, 2019 at 2:14 pm)LastPoet Wrote: I wish I had a physics teacher like you. Mine just throwed stuff in the blackboard and ask about it. I never did homework, but I liked to read my books in the train ride after school. I was so tangled with a simple derivative that when I looked outside I saw my stop going backwards. In the panic I jumped out of the accelerating train resulting in some moderate pain. That,s momentum, gravity and poor decision making in a single lesson.

Pity you weren't taught Einstein's theory of Acceleration Due To Panicking.  I'm sure most of us have got bumps and bruises for ignoring that one.

Boru

The panic must have been on a heroic scale for Mr. Newton’s theory of panicked acceleration to have proven to be wanting.