Exploring Kinetic Energy: Matter Interacting Matter

[coburg]

to add to this discusion could be the fact that energy is a relative quantity...yes...the energy possed by a system is relative to the observer...on close thought this idea will make itself pretty clear...wit this idea in mind...jus hypothetically thinking...can we define as the measure of diffrence between two systems...its jus an opinion...not based on any concerte theory...nevertheless worth a thought

 

[Mk]

energy...something that seems to squeeze everyone's mind...for to tell all the truth...man doesn't know too much abt out energy

I think we do, it seems the mentors and advisors and moderators think they know what they are talking about, its just that not all who read the thread do.

 

[linhtm]

i think energy is fancy world ,we use it apply what we have and what we use

 

[masudr]

What is energy? Easy. Maybe I have an oversimplified view as a physics undergraduate, but here is what I think.

First of all, it is important to treat each model of reality differently, since they are, well, different.

Classical mechanics:
$$E=\frac{1}{2}m\dot{x}^2$$

Relativistic classical mechanics:
First I define the energy-momentum 4-vector:
$$p=m\frac{dx}{d\tau}$$
and define energy as the zeroth component of that vector.

Non-relativistic quantum mechanics:
$$\hat{H}|\Psi\rangle=E|\Psi\rangle$$
where $|\Psi\rangle$ is an eigenvalue of the $\hat{H}$ operator.

 

[bao_ho]

energy is local time

 

[bchui]

Once again we don't seem to have found a satisfactory answer.

Remarkably, we seem to have come to the conclusion that energy isn't real. It only exists in our models and not in reality. How strange that the entirety of physics would depend on something that isn't real? Or am I mistaken?

Yes:!) I agree with you in many sense
For example, in classical Mechanics we have the definitions
$$K.E.={1\over 2}mv^2$$
and $$P.E.= mgx$$ for energy

while $$p=mv$$ for momentum

We can simply think of the [Energy,Momentum] pair $$(E,p)$$ as a transformation rule of the [Displacement,velocity] pair $$(x,v)$$

That happens again in special relativity
[Energy,Momentum] pair is just another way of describing the universe by the [Displacement,Velocity] pair.

That's what "Energy" is about

 

[Dense]

I like to think of energy as the "stuff" that all matter is made of, ultimately. And this is not quite right.

I like to think of energy as the "stuff" that fields are made of. And this is not quite right.

But it helps me wrap my little brain around some concepts.

 

[mtong]

Energy is just a human concept devised to help with our analysis of the physical world.

 

[Galileo]

I don't think the following has been suggested yet.

Every symmetry in physics leads to a conservation law. Energy is that conserved quantity of any closed physical system that results from the time-independence of physical laws.

 

[DaTario]

I would suggest an analysis based on Torricelli equation, which has only to do with the way acceleration causes changes in the square of velocities. Since the concept of force is deeply related to the concept of acceleration, energy emerges.

Best Regards

DaTario

 

[Careful]

I would suggest an analysis based on Torricelli equation, which has only to do with the way acceleration causes changes in the square of velocities. Since the concept of force is deeply related to the concept of acceleration, energy emerges.

Best Regards

DaTario

I did not read the entire thread but here it is:
* energyDIFFERENCES are simply work in Newtonian physics, it does not have any absolute meaning here.
* It is GR which gives energy an absolute observable status through the invariants of the metric tensor, the expansion and rotation scalars of a fluidum etc...

Cheers,

Careful