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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Where does electrical power in PC or other electronic devices goes?

I am wondering where does energy goes for example in PC? As I understand part of it definitely changes to the heat and dissipates, but what about rest of the energy? There is no moving parts except ...
3
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1answer
33 views

Could heat detected from Jupiter's red spot explain the temperature of the Sun's corona?

This is an excerpt from BBC Infrared Telescope, published 27th July 2016 Jupiter's Great Red Spot - a hurricane three times bigger than Earth - is blasting the planet's upper atmosphere with heat, ...
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5answers
109 views

Work as force * distance — what about mass? [on hold]

So, in defining work as force * distance, how is mass applied? Is it just that it's $1kg$ multiplied in normally, but that's typically ignored / not shown? ..so: $2kg \cdot 1n \cdot 1m$ = $2J$ .....
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3answers
86 views

Does electron absorb energy? [on hold]

According to my teacher, an electron is point sized and it does not absorb or release energy. Moreover, my teacher says their orbital absorbs energy rather than the electron. If that is the case, then ...
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2answers
44 views

What frequency is the scratching of finger nails on a blackboard?

This is the frequency/intensity that sets my teeth on edge. Does anybody know what frequency (roughly) it is? I am guessing it is near the top of normal human hearing, 20kHZ, but I'm not sure if ...
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2answers
49 views

Heated and cooled air effects on combustion [duplicate]

In a turbocharged engine, an intercooler is installed to cool down the compressed air (apparently for better combustion). In contrast, in the power plant they use air preheater to heat up the air ...
37
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6answers
6k views

Newton's 3rd law… hitting drywall (which I break) vs hitting a brick (which breaks me)?

According to the Third Newton's law of motion: For every action there is an equal and opposite reaction. So, I understand that if I hit a brick wall with $50\, \mathrm{lbs}$ of force, the ...
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0answers
35 views

Are all kinds of energy quantized? [duplicate]

I was reading this answer of David Z about meaning of "Quantum" that this question came in mind: If light is quantized (i.e. is a integer multiples of some unit $\hbar c/k$), are other kinds of ...
2
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0answers
39 views

When we say particle in a box has quantized energy, is that kinetic or total energy?

In quantum mechanics, it is usually said that energy of the bound (constrained) systems such as particle in a box (infinite potential well) is quantized. It confuses me exactly what type of energy is ...
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1answer
74 views

Energy Spectrum and Gauge Transformations

There is a question in SE about the fact that the Hamiltonian isn't invariant under the EM gauge transformations. I wanted to ask about its consequences here. I know that in general, the Hamiltonian ...
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0answers
27 views

Is there a maximum temperature? [duplicate]

I have read about absolute zero. I understand that it is impossible to cool a system below absolute zero (or to absolute zero for that matter). However, is there a maximum temperature? My intuition ...
3
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2answers
42 views

Does shortening the path length of an excited etalon do work? What about LIGO?

Start with a high-Q etalon excited on-resonance with a laser for a time long enough that it has built up an essentially stable standing wave. There is a constant outwards-directed force on each mirror,...
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0answers
31 views

Minimum gap between consecutive energy levels?

Assume a standard one-particle, non-relativistic Hamiltonian of the form \begin{equation} H=\frac{p^2}{2m}+V(r) \end{equation} and denote its eigenvalues as $E_{n,\tau}$, where $n$ is the principal ...
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1answer
57 views

Doesn't quantum uncertainty disprove string theory? [duplicate]

String theory states that the oscillations of little strings are responsible for all the particles in and the evolution of the universe. The specific type of particle created by a string depends on ...
0
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1answer
32 views

Is the energy cost of desalination linear vs salinity? [closed]

There is a practical limit to how salty water can be and still have a useful potential for desalination. For example, a recent study on the potential for water recover from known sources on Mars ...
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0answers
24 views

Stuck with 2D kinetics problem [closed]

I've been trying to solve this exercise for the last four hours and I'm totally stuck. The problems goes like this: Given the mechanism in the image, located in the vertical plane, the OB cord ...
0
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1answer
20 views

how does an induced draft fan work in a coal

I have been studying a coal-fired power plant, and the power plant cycle has an induced draft fan that is used to create negative pressure to help get the flue gas travel to the stack. I am confused ...
3
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1answer
32 views

What is the root mean square energy of a nucleon bound within a nucleus?

How does the root mean square energy of a nucleon in a nucleus of atomic mass number A in the ground state depend on A ?
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1answer
61 views

In relativity theory could we talk energy rather than frames of reference? [closed]

In relativity theory, the space geometry, of space and time, is no longer absolute, if one observer is accelerating compared to the other. Could I say in other words that space geometry is changed if,...
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1answer
58 views

Proper definition of Internal energy

In Internal energy of a gas ($U$), we have to include ALL types of energies possible like $KE$, bond energies, nuclear interaction energies, etc.., However we have derived that $U = (f/2)nRT$ from ...
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1answer
28 views

Conservation of Energy with Rotation Caused by Friction

A book that I am using to study poses the following problem: Suppose you wish to use a spring with a force constant $k$ to launch a spherical ball or radius $r$ and mass $m$ up a ramp of inclination ...
2
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0answers
26 views

If a wormhole connects between ground and sky, does an object require extra energy to pass through it? [duplicate]

As we know, if we bring an object from ground to sky (higher position) by normal methods, extra energy is required to overcome the gravitational potential energy. Then if a wormhole connects between ...
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0answers
24 views

How would I go about calculating the frequency and amplitude of a sound produced by a collision?

How would I go about calculating the sound pressure level, frequency and amplitude of a sound caused by a collision, given the velocities of the two objects colliding, their acceleration, densities, ...
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2answers
53 views

Is energy only transmitted through electromagnetic and particle radiations? [closed]

Which are the other ways of transmission if any? If energy does not require any medium for transmission(as for sunlight reaching earth, the heat too), is it transmitted in quanta in particle radiation ...
0
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1answer
53 views

What is the capacity of an electron to absorb energy? [closed]

When an electron get excited we find that electron absorbs energy and jumps to the required shell. This means that electron can absorb an infinite amount of energy and can get excited to infinity ...
3
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1answer
99 views

How does eating a cold ice cream actually heat up your body? [closed]

The question is the title itself. During winter one of my friend told we'll have an ice cream. And rest of us where like are you nuts. He was like cold ice-cream actually heats up your body. Even I ...
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2answers
47 views

Do radio waves from the Sun reach Earth?

Do radio waves from the Sun come into contact with Earth? If so, do they penetrate the atmosphere or are they reflected, absorbed, or scattered?
3
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1answer
32 views

Black body radiation and number of photons emitted

Usually the black body radiation (at a certain temperature $T$) is given by $$\rho ( \nu ) = \frac{8 \pi h \nu^3}{c^3 \left( e^{h \nu / (k_B T)} - 1 \right)}$$ This quantity $\rho ( \nu )$ should be ...
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0answers
16 views

Bernoulli equation: energy conservation in moving reference frames

I get a bit confuse with the use of Bernoulli equation in moving (inertial) frames. Consider the following example. The tube in picture is moved with velocity $u$ inside a tube where fluid moves with ...
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2answers
20 views

Vertical and Horizontal Oscillations With the same period and speeds

Why do vertical and horizontal springs with the same masses attached oscillate with the same period and the same speeds at matching positions? Assume that the horizontal surface is frictionless and ...
-1
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1answer
41 views

What is the maximum amount of electricity I can draw in 48 hours from a domestic supply? [closed]

An electricity company is offering free electricity for a 48 hour period every week. The rate the rest of the time is very expensive. How much power can be drawn from a domestic UK supply? Would it ...
1
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1answer
36 views

What is the average range of voltage of lightning in sky?

I wondered how much energy is required to produce , such a loud sound? What is the average range of voltage in sky? Is there any possible way to store it ,and use when needed?
14
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4answers
681 views

Increasing a potential causes increase in energy levels

Suppose a potential $V(x)$, and suppose a bound particle so the allowed energy levels are discrete. Suppose a second potential $\widetilde{V}(x)$ such that $\widetilde{V}(x) \geq V(x)$ for all $x$ (...
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3answers
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Can we run out of gravitational (tidal) energy?

I read an article on energy forms and sources that made me think. Energy comes from somewhere and is limited in various senses. It's most obvious for fuels: we burn coal and oil and at some point we'...
2
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1answer
113 views

Why are general wave functions expressed in terms of energy eigenfunctions?

I have read that the eigenfunctions of any hermitian operator can be used as a basis to express any function, but I have only ever really seen the eigenfunctions of the Hamiltonian used. Why is this? ...
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2answers
90 views

Can Light Really be Matter? [closed]

I remember during my early education being taught that light is a form of matter. This has always seemed counter-intuitive to me.
3
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2answers
38 views

A question on the redshift of photons due to cosmic expansion

Given that the universe is expanding over time, in the sense that the (spatial) metric is changing over time, corresponding to the physical distance between objects increasing, naïve intuition leads ...
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4answers
104 views

Why don't high pressure gases stored in containers lose energy?

Containers holding gas at a high pressure don't slowly lose the internal energy of the gas. It seems like the high speed particles would collide with the metal walls and slowly transfer their energy ...
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0answers
42 views

Can energy go through higher dimensions?

It is hypothetically predicted that gravitons can escape from the 4th dimension or brane and "leak" or go through higher dimensions. I wonder if energy can do the same thing. Is there any explanation ...
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0answers
13 views

Is there a way to calculate the change in temperature of water in a vacuum?

My understanding is that water boils when the vapor pressure is reached and then, at some point, freezes. Is there a way to relate the vacuum pressure to the temperature of the water until it changes ...
0
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1answer
28 views

Photon frequency [duplicate]

I understand frequency depicted as an oscillation over time, (sound pressure, pendulum swing, etc.). What then can be meant by the frequency of a photon, which we think of as traveling in a straight ...
1
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1answer
38 views

Einstein coefficients for emission/absorption and energy density

When dealing with a system of two energy levels $E_1$ and $E_2$ in laser theory, the following rate equations are written: $$\frac{d N_1}{dt} = A_{21}N_2 - B_{12} \rho ( \nu ) N_1 + B_{21} \rho ( \nu ...
4
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1answer
95 views

Energy Spectrum of Star Products

We have that a property of the transition operator defining c-equivalence (or star equivalence from equation 1 in Bertelson) is \begin{align*} T(f\star_Mg)=T(f)\star'T(g)\,, \end{align*} where $\...
17
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3answers
550 views
+100

trouble reconciling doppler shift for energy and momentum of light

[See late addition at bottom for what currently remains unresolved in this question.] I have seen the assertion in a couple of places that if you trap light in a reflective resonator, or any other ...
3
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1answer
74 views

Mass dropped on a spring

I thought this would be a particularly simple problem but it is turning out to be quite the opposite. I am sure I am doing a very simple mistake. The problem statement is that there is a mass which ...
-3
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1answer
100 views

How is hydrogen fine structure currently accounted for? [closed]

At a usually reliable site, Hyperphysics, the fine structure of Hydrogen is accounted for by the interaction between the B-field generated by the orbit of the electron, $0.4\:\mathrm{T}$ at $1s$ and $...
1
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1answer
66 views

is the sun going to make an electromagnetic pulse in the next 50 years?

EMP is very damaging and can cause blackouts and other bad results specially on electronic devices , so i heard that our sun is going to make an electromagnetic pulse during the next 50 years ..is ...
1
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1answer
16 views

Why is it that only thermal energy is available in a particle propagating throughout a space-charge layer in a plasma (not kinetic)?

In this PDF on page 5 the author explains that a particle moving through a space-charge (electron density in a plasma) gains only thermal energy. Should there not also be kinetic energy?
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2answers
45 views

Do induction chargers waste electricity?

Do induction chargers use more energy than traditional chargers while plugged in to the mains but not charging a device?
2
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1answer
52 views

Is there a theorem which specifies the state (with energy $E$) with maximum entanglement? [closed]

Does there exist any theorem in quantum information which states that the particular state with energy $E$ is the state with maximum entanglement (or discord) among all possible state with the same ...