Questions tagged [energy]
Energy is the conserved quantity associated to time-translation invariance and represents the work a system is capable of doing. Use this tag for questions about energy, and consider adding the [energy-conservation] tag if it is specifically about its conservation.
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Do blueshifted and redshifted light sources have differing energies?
The thought experiment:
Two spaceships are passing each other some distance from a star. Both ships are at relativistic speed, one toward and one away from the star. Should the total energy observed ...
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Zero Energy and Zero Mass
It is a general principle in modern physics that there is no true zero point for energy. A system's energy states can be listed from higher to lower, and one can be assigned "0" by arbitrary ...
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Confused about the Kinetic Energies of a many-body system
My Question stems from the following problem:
Consider two resting Point Masses, each with mass $m$, which are connected (the connection having no mass). A Force $F$, which is always perpendicular to ...
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Black hole evaporation [duplicate]
“If mass and energy are equivalent, and black holes evaporate by losing energy via Hawking radiation, does that mean singularities never actually form — that they’re replaced by ultra-dense, finite ...
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How does Energy Enter Chemical Potential?
Energy should enter the chemical potential as:
$$\mu N = U - TS + pV\;,$$
that is, with a positive sign. That means that if I add a potential (energy per particle) of $\phi$, then the energy should ...
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Questions about fusion energy and binding energy per nucleon
I have 2 confusions about this binding energy graph for atoms
I keep on reading that fusing nucleons up until Fe-56 doesn’t cost energy and only releases binding energy. However, I understood that ...
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Is A/C (Air Conditioner ) consider as reverse entropy? [closed]
Can we consider the air condition as reversing entropy? what are the other process like that?
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Why does the particle in a box have increasing energy separation versus the harmonic oscillator having equal energy separations?
This is referring to the one-dimensional particle-in-a-box model. I know that mathematically, the energy is a quadratic function of $n$, so it causes an increasing energy separation as you reach ...
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Why is such heat transfer necessarily quasi-static?
I am reading p. 101 in the second edition of Callen's Thermodynamics and an Introduction to Thermostatics, and I am a little confused. I understand that a quasi-static process is a transformation ...
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How can we define total energy and rest energy in relativistic energy equation?
I have learned that, derivation of mass-energy equivalence leads to $K=\gamma mc^2 -mc^2$, and it means that $\gamma mc^2$ is the total energy and $mc^2$ is the rest energy. But doesn't this equation ...
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Does Rotational Kinetic Energy Influence Gas Temperature, or Is It Solely Defined by Translational Motion?
In kinetic theory, the temperature of a gas is traditionally defined through its translational kinetic energy, using the relation:
$$K.E. = \frac{3}{2} kT \ .$$
This definition appears to imply, that ...
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Is energy in the future consumed when the waves interfering?
Let’s suppose there are 2 sound sources with nothing around. The waves they send have opposite phase so in the middle, the wave is constructive and on the other side it’s destructive, like what ...
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Why does temperature increase mass?
We learn that $E_0=mc^2$, that is, internal energy is a form of mass. Also, kinetic energy does not relate to mass at all, and the complete relativistic energy momentum equation is
$$
E^2=(mc^2)^2+(pc)...
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Does the energy of lights change when two lights combine? [closed]
This question comes from a imagination of mine. If there are 2 laser light sources that are totally the same, which means the amplitude, wavelength, and phase of the two lights are equal. Let’s assume ...
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How were early thermodynamicists able to measure heat if they didn't already know internal energy was a function of state?
I am reading the following excerpt from this bachelor thesis:
THE FIRST LAW: For any cyclic process $\mathcal C$, the amount of heat $Q(\mathcal C)$ absorbed by the system is proportional to the work $...
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Uncertainty Principle and boundedness of the Hamiltonian
In then statistical mechanics book by R.K. Pathria & P.D. Beale (page 82-3rd edition), while discussing positive/negative temperatures, the author states:
"the uncertainty principle alone is ...
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What's the philosophical understanding of work, energy, conservative forces? [closed]
I have a particular way of studying physics- I focus on building the philosophical understanding of each idea/concept without using any math/formulae. Once I feel confident enough in my understanding, ...
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Relation between momentum and "center of energy" in special relativity [duplicate]
In newtonian mechanics, we have $\vec{P_{tot}}=M\vec{V_{CM}}$ for a system of particles.
On page 546 of Griffiths' electrodynamics, he mentions that in special relativity, we have $$\vec{P_{tot}}=\...
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Could momentum exist without energy?
I just came up with an interesting idea whether we can create a pure “magnetic gravity”. It’s just like a conducting coil produces only magnetic fields because the positive and negative charges are of ...
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Is work being done as the universe is expanding?
As the universe is expanding is work being done? If so, where is the energy coming from?
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Does heat pump work more efficiently than electric heater? [duplicate]
My question comes from another very simple question: If I want to heat my house by a electric heater or a heat pump driven by electricity, which cost me more? As far as I've learned, the efficiency of ...
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Does the energy-time uncertainty hold for a volume and macroscopic objects?
I'm wondering whether the energy-time uncertainty relation $$\triangle E \triangle t \geq \hbar /2$$ can be applied to the energy state of an object, say some object of side length $L$, where the time ...
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Why is grid-wide battery storage capacity measured in units of power instead of energy?
A battery stores energy, not power. It would not make any sense for something to "store power", because power is not a conserved quantity.
Therefore, the energy storage capacity of an ...
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Energy and momentum of electromagnetic field generated by a moving particle with constant velocity
I calculated the energy and momentum of electromagnetic field generated by a moving particle with constant velocity $v\hat{z}$ using the general solution of Maxwell's equation. A particle of charge $q$...
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Derivative of energy needed to keep an object at constant acceleration
Imagine I want to keep a 10kg object at constant acceleration? What is the derivative of energy (with respect to time) that I need and what is it's value?
I know about P=Fv. This equation shows that ...
