Energy is a quantity which gives an overview of the amount of work doable by the system.

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Determine the particle velocity of a pressure wave

I am using constant density wave propagators to model seismic waves in the subsurface. What I want with these acoustic waves is to estimate the energy of them at a certain grid point at a given time. ...
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46 views

What physics considerations direct the charging of cars with wireless?

Is there any frequency at which cars can be charged with using wireless? Surely, wireless transmission can be safely assumed to be a form of energy transfer, and there can be charging of cars without ...
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140 views

Energy of gravitation

EDIT: As some confusion has appeared, I want to make another clear question. If gravitational energy is meaningless in general relativity (since it is the geometry), how can one come up with the ...
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1answer
69 views

Relationship between temperature and energy

What is the definition of temperature in relation to energy? I'm mostly interested in general dimensional terms. Is temperature the kinetic energy per mass? Or kinetic energy per volume?
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237 views

Why are the energy eigenstates realized in atomic transitions?

I have a question like "Why is it often assumed that particles are found in energy eigenstates?", it is a little different, though. When one solves the hydrogen atom, one can use a polynomial Ansatz ...
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1answer
58 views

Why do safety helmets have a softer inner layer nearer the head?

I know that when an object collides onto the helmet, it causes an inelastic collision so that energy is absorbed by the structure of the helmet, so what exactly does the softer inner layer do? Does it ...
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3answers
88 views

How can gravity affect light?

I understand that a black hole bends the fabric of space time to a point that no object can escape. I understand that light travels in a straight line along spacetime unless distorted by gravity. If ...
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3answers
95 views

Is the energy of a photon continuous/discrete?

I was struggling today with this question: does a free photon have a continuous energy spectra? Free means in no context of any energy system (eg. an atom, em field). Although I'm asking myself if ...
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134 views

How do photons know they can or can't excite electrons?

This might be a stupid question, but nonetheless, it has been bothering me. If you take a photon, make it go through some atoms in a solid, liquid or whatever, then you have the chance of this photon ...
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101 views

How much work will a human do to lift a weight?

I saw a pretty simple homework question here that asked how much work it takes to lift a 200 kg weight, and while the math for a basic answer is simple the weightlifter in me instead wanted to ...
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126 views

Is there a fundamental particle that gives rise to energy?

I was wondering if there exist a particle analogous to the Higgs boson that gives rise to energy, I´m sorry it´s not the big question but I feel confused about how the universe works, also I have been ...
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1answer
175 views

Intuitive reasoning for why short wavelength photons pack more energy?

The energy equation is straight forward, yes, but is there an intuitive reason for this?
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21 views

Could symmetric molecular stretching cause a physical object to become amorphous? [closed]

I understand very little of this, but my google-foo has yielded me next to nothing, I thought I might then just ask. My real question here is if it might be possible through the use of vibration to ...
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194 views

Where do flying gas molecules get their energy from?

If you heat up water in a tank to boiling point, some of the water will turn to steam. Gas bubbles are created in the water. According to Archimedes principle, the gas bubbles will have a force equal ...
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1answer
43 views

How to work out the work done to put a satellite into orbit?

I'm having troubles doing questions that involve how to put a satellite into orbit. So we have a satellite in orbit 20500 km above earth, (and earth radius = 6380 km), the satellites mass is 1000 kg, ...
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2answers
50 views

Work and Kinetic energy rely on each other which came first?

In all the places I've looked kinetic energy is derived from the definition of work, but I don't understand how the definition of work was developed with out the concept of kinetic energy. My question ...
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1answer
28 views

Amplitude decrease during geometrical spreading of a seismic pulse

I'm looking at amplitude decrease of a seismic pulse as a result of geometrical spreading. Starting with the energy contained in a unit area, $I = E / (4 \pi r^2)$, where $E$ is the original energy ...
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2answers
1k views

Energon: is it possible?

I'm always quite curious about the "Energy cube" in Transformers, or namely Energon. Is it really possible to store energy, such as electricity, into such a compact form? safe to distribution, and ...
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1answer
21 views

Why does absorption cause seismic pulses to increase in length over distance?

The specific question I'm trying to answer is "How does the progressive loss of higher frequencies in a propagating seismic pulse lead to an increase in pulse length?" I understand how the higher ...
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1answer
48 views

Transmission/Equilibrium Question

Suppose there are two wheels linked by some kind of apparatus with a transmission, in a vacuum. Wheel A is spinning, wheel B is not. Is it empirically possible for the transmission to transfer the ...
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2answers
90 views

Bloch theorem, Energy, Free electron

I'm trying to learn on my own a bit of solid physics to tackle semiconductors afterwards. I'm struggling with the Energy versus $k$ diagrams for a free electron which shows that for a single value of ...
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1answer
84 views

Kinetic energy and potential energy variation over distance in SHM

When you compute the average potential energy of a horizontal spring mass system from the mean position to the positive amplitude A, the value comes out to be $\frac{1}{6}kA^2$. For the average ...
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55 views

Compute energy from displacement via time integration (using ODE)

How to compute energy from displacement given by solving an ODE via, e.g., ODE45. Say one has: $$ \ddot{z}+\zeta \dot{z}+z=\kappa\cos\left(\Omega t\right),\quad z=z\left(t\right) $$ and wishes to ...
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1answer
39 views

How do you calculate the power needed to keep something stationary? [duplicate]

1) If I place an object on a table, it will sit there forever. There's no change in potential or kinetic energy. If I hold the object at the end of my outstretched arm, eventually I can't do it ...
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1answer
57 views

Why is the D+T fuel inside a pellet in two distintic regions in fusion after compression

Could anyone explain why the D+T inside the pellet is in two distinct regions? And why the center is a lot less dense than the outside region? I have been trying to find answers online but i cant ...
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1answer
41 views

The formation of shockwave inside pellets in inertial confinement fusion

In the explanations i have read on the internet about ICF they all explain that the top layer of the pellet or the ablator is heated till it explodes and this produces a reaction force which compress ...
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1answer
60 views

Time Energy symmetry in General Relativity (not asking about energy conservation)

In General Relativity is there a TE symmetry similar to CPT symmetry in the Standard Model ? It's pretty easy to understand that by flipping charge and parity you merely get a time reversed equivalent ...
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39 views

Derivation of Van der Waal's Equation from Helmholtz Free Energy

From the following equation $$ f(T,v) = f_{id}(T,v) - RT \ln\bigg(1-\frac{b}{v}\bigg)-\frac{a}{v}$$ how do I derive Van der Waal's equation. In the equation above, $f$ and $f_{id}$ are the Helmholtz ...
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55 views

Faraday Effect does light bend or lose energy?

I was reading upon Faraday effect when it said Faraday effect causes a rotation of the plane of polarization That in mind, does this mean the light can be bent around or does the light loose ...
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1answer
107 views

Sufficient conditions for the energy to be not conserved?

I'm almost embarrased to ask this question because I thought I was by now very confident with classical mechanics. Someone has stated that given a mechanical system with a Lagrangian $L$ s.t. ...
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4answers
78 views

Is work done by how much velocity is changed or how much displacement is done?

A sailboat is moving at a constant velocity. Is work being done by a net external force acting on the boat? The answer key is "No" according to the work energy theorem about work is done when ...
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1answer
32 views

Energy comparison, evaporate water vs compress air, same mass

I would like to compare the energy requirements of the 2 following tasks: Total energy to evaporate 1 litre of water at normal atmospheric pressure at normal temperature? Total energy to compress ...
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0answers
50 views

Intuitively proof that intensity of a wave is proportional to the square of its amplitude [duplicate]

Firstly I would like to know if this is valid for every kind of wave, or are there any conditions/exceptions where this is not valid. But the main question is, is it possible to prove this fact for a ...
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3answers
108 views

Do massless particles follow the curved spacetime or not?

I am assuming that zero (rest) mass particles don't interact gravitationally with each other and other particles. Does that mean they experience a "flat" spacetime instead of a curved one? I find it a ...
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490 views

What is “Energy” of a vacuum in the context of quantum theory?

I'm not a physicist or cosmologist, so I hope I am asking the right question with the right words here. My question regards the word "energy" as it pertains to quantum vacuum states, and to concepts ...
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3answers
125 views

Where is the potential energy due to internal interactions in total energy?

In thermodynamics the total energy of a system consists of kinetic energy of motion of the system as a whole, potential energy of the system as a whole due to external force fields, and energy ...
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2answers
186 views

Why does blowing on hot coffee cool it down?

And will it cool off faster if you blow across the top of the cup or directly into the coffee? Does it have to do with the fact that when you blow across the top of the cup the velocity of the air ...
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29 views

Polarizable molecule in E-field

If we have a linear molecule with a dipole moment $\mu$ in a static electric field $E$, the potential is given by $V = - \langle \mu,E \rangle$. What is the appropriate equation for the potential if ...
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1answer
38 views

Is Red-Shift experiment correct?

I been reading: http://www.mth.uct.ac.za/omei/gr/chap5/node2.html. The website seems credible with its contact details & location being extremely accurate and easily verified, and its mathematics ...
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1answer
35 views

How do I describe the energy an electron gains (and loses) in a circuit?

I am looking at the simple circumstance of an electron traveling through a long wire by a potential. I see how one would be motivated to use the usual formula, W=F*d, to describe the electron's net ...
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131 views

Magnet motor free energy generator [duplicate]

Is it possible to run a fan without electricity? like the one show on this website? http://free-energi.com/index.php?a=2
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2answers
63 views

Changing from potential to kinetic energy

During a conversation with a friend, I began to wonder if there's is a term for the transformation of potential energy to kinetic energy, and vice versa.Is there a term for the process of converting ...
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1answer
61 views

How to calculate energy to start movement?

So let me try to explain a little bit. Lets say I have a robot on wheels. I want this robot to push a block. Lets say the force to produce in order to move that block is 100N. How much energy will I ...
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1answer
90 views

Conservation of energy and momentum via the continuity equation in asymmetric time and space translation

I am confused about energy and momentum conservation, time and space translation symmetry, and the continuity equation. Suppose we have a mass $m$ in inertial space far from any gravitational ...
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2answers
55 views

Turbine like device in space spinning with KE and converting to Watts. Acceleration is constant?

I have a question that I can't seem to get my head around. I'm really rusty on my physics, but I'm sitting here trying to think this out, but I'm missing a really big part of the equation. So lets ...
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33 views

Radius dependence of Energy levels of spherical Quantum dots

I have frequently read in articles that the energy level of spherical quantum dots depends on radius. We simply match the wave functions inside and outside the particle and find the intersection of ...
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49 views

Does a rotating plank only acquire rotational kinetic energy?

I have another doubt with a Kleppner problem :(. A thin plank of mass M and length l is pivoted at one end. The plank is released at 60$^{\circ}$ from the vertical. What is the magnitude and ...
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1answer
24 views

Calculate amount of energy based on height of object

How can you calculate the amount of energy an object produces that falls from a particular height? Or water. In an eg i would like to know how can you calculate the amount of electricity water can ...
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2answers
91 views

Can matter be created from energy? [duplicate]

The small, hot, dense early universe the size of an atom was made up entirely of energy, it wasn't until after the expansion began and the universe cooled down some of that energy began converting ...
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173 views

Classical vs. quantum energy of the hydrogen atom

If I have an electron and a proton and calculate the classical energy which I get by bringing the electron from infinity to the distance of a Bohr radius to the proton, I get 27.2 eV, but the electron ...