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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 [tag:energy-conservation] if it is specifically about its conservation.

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Does the energy of two entangled quanta vary with distance?

my question is about,Does the energy of two entangled quanta vary with distance?
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47 views

Is There a Limit to The Energy-density Confined to a Black-hole Structure, Consisting of a Schwarzschild Sphere? [closed]

Imagine two particles repeatedly colliding with increasing momentum,like a dense collection of particles confined within the envelope of a collapsing star that's close to becoming a black hole. Is ...
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1answer
67 views

Energy spacetime warping

If energy warps spacetime, then does light warp spacetime? And if special relativity says that things near the speed of light increase in relativistic mass, then does light have a relativistic mass? ...
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2answers
56 views

What is the energy of an atomic orbital?

When we refer to energy of an atomic orbital what is this energy ? is potential energy ? but if is potential energy then shouldn't be considered the whole potential energy of the atom ( potential ...
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1answer
41 views

Irreversible and reversible compression work

Why is work done on the gas when it is compressed from (p2,V2) (pressure,volume) to (p1,V1) against constant pressure external pressure p1 maximum when it is done irreversibly? In reversible process, ...
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1answer
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Formula for Power from Kinetic Energy

Work Done = $Fd$ Power = $Fv$ If the (net) Work Done = Change in Kinetic Energy, and the object starts from rest: Work Done = $\frac{1}{2} mv^2$ Power = $\frac{1}{2} m av$ Power = $\frac{1}{2} ...
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3answers
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Photon energy comes in packets

From the HyperPhysics page on the Photoelectric Effect: According to the Planck hypothesis, all electromagnetic radiation is quantized and occurs in finite "bundles" of energy which we call photons....
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2answers
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Constant gravitational acceleration $g$ and energy

I've been taught that $g$ is constant for different masses and that if I were to drop a heavy object and a light object from the same height then they would reach the ground at the same instant with ...
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49 views

Generic Differential Equation for Oberth Effect

In Wikipedia article about Oberth Effect there is an example of calculation in a simple case when the differential equation is not required. In non-English versions of this article (for example, ...
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3answers
60 views

How are various forms of energy ability to do work? [closed]

According to various sources that i have come across, energy is the ability to do work. Can someone elaborate how diff forms of energy like potential energy and kinetic energy are ability to do work? ...
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4answers
86 views

$E=hf$ true for all implies $E=pv$ true for all?

In the answer to this question: Can I apply $E=hf$ to a particle having mass? It was stated that $E=hf$ is true for all particles. If so, doesn't this imply that $E=$momentum x velocity is true for ...
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1answer
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Work done in accelerating an object in circular motion

In a hammer throw competition, an athlete spins a “hammer” before releasing it. The “hammer” used in this sport is a metal ball of mass 𝑀 = 8 kg and diameter 𝐷 = 30cm, which is attached to a ...
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1answer
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How to estimate energy of piezo ignighter discharge?

Question for fun. All we know piezo ignighters, these small friends, like following one: They are of quite same size and parameters with rough approximations: same spring, same piezo, same hit force, ...
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3answers
73 views

Does the wave function carry energy and momenta?

I was reading a forum regarding the reality of the wave function, and one user (who apparently works in quantum foundations) stated that "the wavefunction carries no energy or momenta and this ...
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0answers
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Is this solution in Conquering the Physics GRE incorrect? [closed]

In Conquering the Physics GRE 2nd edition, Exam 3 problem 20, the statement is as follows: A metal bar is pulled at constant velocity $v\mathbf{\hat{x}}$ along two metal rails a distance $d$ apart ...
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1answer
47 views

Cycling: The energy behind it

I'm developing a school project (I'm studying software engineering) and it's about a sharing bicycles company. We need to calculate the total amount of necessary energy to travel from one point to ...
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3answers
95 views

How can we define energy other than the definition that it's a capability to do work? [closed]

It is actually a property of energy that it can do some work not an actual mean to define it because we cannot define a thing on the basis of what it is doing or what it can do.
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1answer
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Joule expansion and center of mass

This question comes from a doubt resulting from some physics forums. Similar to and related to this question, I have a doubt on Joule expansion raised by reading too much bad faith arguments. I'm not ...
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2answers
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What's the total energy when I tie a mass with a string and then rotate it in a radius $r$ with angular velocity $\omega$?

I know it may be a very silly question. But when we are calculating the total energy, shouldn't we also consider the potential energy due to the centrifugal force acting on the body? Or as, we are ...
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2answers
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Is it possible to add energy to an antiparticle?

The title says most of it but the more drawn out version is. If you were to add energy to a single particle or antiparticle in a pair, what would be the effects, if it is possible to do.
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1answer
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Why Gibbs energy for nucleation theory?

In nucleation theory, the free energy is given by (https://en.wikipedia.org/wiki/Classical_nucleation_theory but in many other places also): $$\Delta G=\frac{4\pi }{3}r^3\Delta g +4\pi r^2\sigma,$$ ...
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1answer
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Whether this proof regarding Bohr's second postulate is true or false?

Let us assume a particle oscillating with displacement $x$. Now $x = A\sin(2πft)$ $$\frac{\mathrm d x}{\mathrm dt} = v = 2πfA\cos(2πft)$$ Now $KE_\text{max}$ can be given when cosine value is 1; ...
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2answers
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Inconsistent Results with Momentum and Kinetic Energy

A speed skater with a mass of $m_1$ kg is moving at $v_{1i}$ m/s. He prepares to push the next speed skater of mass $m_2$ kg moving at $v_{2i}$ m/s. After the push, the velocity of the first skater ...
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2answers
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Proof for $W_{\text{total}}$

Looking upon a certain solution of a problem in Griffiths regarding the work done in arranging two concentric spheres with inner shell having charge $q$ and outer shell with charge $-q$ and I found a ...
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2answers
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Error of relativistic kinetic energy

I have recently begun working on the special relativity theory. I have then made the taylor series for the gamma factor to show that we get the classic formula for kinetic energy: $$E _ { k i n } = m ...
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3answers
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What is the “lowest energy”?

In many textbooks I come across the term lowest energy. For example in atomic structures, electrons are placed in orbitals in order for the atom to have the lowest energy. But what is this energy? ...
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4answers
351 views

Can potential energy be the sum of the work done by all forces?

I often see that the total energy of a system is the sum of potential energy+ kinetic energy. Is it always like that? Could I say that the total energy of a system is the sum of the work of all force +...
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2answers
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How can a stiffness of a spring can be $k(x+x^3)$? Compute energy total of the system [closed]

Consider the motion of a particle of mass $m$ attached to a spring of stiffness $k(x+x^3)$ where $x$ is the displacement. 1) How can look such a spring? I thought that the stiffness of a spring ...
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2answers
62 views

What does the term $e^{-h\nu /kT}$ in Boltzmann distribution function mean and what roles does it play? [duplicate]

What is the physical meaning of $e^{-h\nu /kT}$ in the Boltzmann distribution function. I am aware that $h\nu$ represents energy of a photon and $kT$ is the thermal energy available to the system. I ...
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48 views

Why should vacuum energy be zero for LSZ formalism?

Can anyone explain why vacuum energy must be zero if we are to use LSZ formalism?
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5answers
76 views

Conservation of Mechanical Energy in moving frame

A ball of mass $m$ is attached to a spring that is attached to a heavy moving cart (mass of cart $M >>$ mass of ball $m$) moving at velocity $V0$. The compressed spring with known spring ...
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4answers
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Does the total kinetic energy change during an elastic collision?

If two balls of same mass with speed $v$ and $-v$ undergo an elastic collision, the kinetic energy will be the same after the collision as before. However, during the collision, does it also remain ...
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4answers
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Does a particle with infinite energy escape an infinite well?

Currently, my modern physics class is going over particles in finite and infinite wells, general quantum formalism, and tunneling. What happens to a particle as it gains an infinite amount of energy? ...
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Negative Eigenvalues of the Hessian

I am calculating the eigenvalues of the Hessian for a ferromagnetic system. My energy has the zeeman term, a nearest neighbor exchange term, and a dipole-dipole term. I create the hessian where my ...
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2answers
108 views

The allowed energies of 3D harmonic oscillator [closed]

I'm trying to calculate the allowed energies of each state for 3D harmonic oscillator. $$ E_n = (n_x+\textstyle\frac{1}{2})\hbar \omega_x+ (n_y+\textstyle\frac{1}{2})\hbar\omega_y+ (n_z+\textstyle\...
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1answer
49 views

Work-Energy Theorem for Non-Constant Mass

"The net work done on an object is equal to its change in kinetic energy." Let's say that a rocket is moving upwards while expelling gas and is thus losing mass. (Non-constant mass) As the object ...
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A short question regarding Hamiltonian [duplicate]

Can any one please tell me in what cases the hamiltonian is not Equal to Total energy. My guess, albeit educated, is if the potential is either a function of time explicitly or a function of velocity, ...
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0answers
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What is the energy loss when charging a phone battery with another battery [closed]

I'm curious to find out what the energy loss is when an external battery pack charges up another battery, say one in a mobile phone. Say my phone's battery has a capacity of 1000 mAh, and my ...
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3answers
60 views

How are these two definitions of energy related/derive from each other? [closed]

How are these two definitions of energy related/derive from each other: $$E = \frac{mc^2} {\sqrt{(1 - v^2/c^2)}}$$ vs. $$E = \sqrt{m^2c^4 + p^2c^2}~?$$ Both equations express the relation between ...
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1answer
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What percent of the Black Hole energy is in the gravitational field significantly outside the event horizon?

This question is sparked with an answer to another one. We know that fields have mass-energy and gravitational field is no exception, some share of BH mass should be contributed by its gravitational ...
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0answers
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Does ABS increase the breaking distance of a car? [closed]

Question: Can an ABS (Anti-lock Braking System) instead of decreasing the breaking distance actually increase it? If yes, is this its general behaviour, or only in specific circumstances? Wikipedia ...
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2answers
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How much energy is wasted by a noisy refrigerator?

I recently bought a new refrigerator for my kitchen. The feet are adjustable but I've been lazy. Whenever the motor runs and the feet aren't all touching the floor there is a loud buzzing noise. As ...
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2answers
99 views

Meaning of $E$ in time-independent Schrödinger's Equation (high school)

I've just learned the time-independent Schrödinger's equation as $$-\frac{\hbar^2}{2m}\cfrac{d^2\psi(x)}{dx^2}+V(x)\psi(x)=E\psi(x).$$ Does $E\psi(x)$ mean that $E$ is a constant (that the kinetic ...
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1answer
37 views

Potential energy of the oscillator

Is there a difference between the potential energy of an oscillator and the potential energy of the spring which is associated with? When we compress a spring horizontally without any object ...
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1answer
74 views

Finding an energy of a particle in an infinite potential well

This question arises from a discussion I recently had with my friend. We were talking about a particle in an infinite potential well. The particle is in an arbitrary wavefunction $\Psi$. When one ...
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1answer
79 views

Does a non-spherical black hole have distribution of mass like an empty body, solid body or pointed object?

Suppose a non-spherical (say, rotating or under distortion of another gravity source) black hole. Does it have its mass distributed as if all the mass was on its surface, or as if the mass were ...
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1answer
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Which direction will this object move in at the end of this process?

1) Consider an object with no net force acting on it moving with a constant velocity v. It has a momentum mv. 2) Now let a force F1 act on the object. Let the direction of this force be opposite (to ...
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2answers
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Gravity in classical energy

It's well understood that matter has mass, and more importantly gravity. I believe I am correct to say that gravity is more like an affect of matter. And not actually part of it. Ie mass bends space ...
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Energy of bound states in gauge theories

In gauge theories such as QED or QCD, are the rest energies, and therefore the invariant masses, of various bound states, such as those of positronium or charmonium, gauge-invariant observable ...
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4answers
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In what context is enthalpy a convenient concept?

Internal energy $U$ is clearly an important concept; the first law of thermodynamics states that for an isolated system internal energy is constant $(\Delta U=0)$ and that for a closed system the ...