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

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Extra energy in quantum tunneling

In quantum tunneling, the probability of finding an electron inside the potential barrier is non zero (http://i.stack.imgur.com/v8Kr1.gif). So we can actually find an electron which had an energy E in ...
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314 views

What are the forms of energy at fundamental level?

Most high school textbooks distinguish several forms of energy. Mechanical: -Kinetic -Potential Chemical Electromagnetic Nuclear Gravitational Thermal Hydraulic Electric Mass ... This ...
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91 views

How is the energy of a lightning calculated?

I was wondering how is the energy of a lightning measured? Is it based on the luminous intensity and/or the generated sound? What about the generated heat and energy spent in the production of ozone? ...
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1answer
133 views

Does a 27 hp engine output the same amount of energy as lifting a 1 ton stone block almost 3 meters per second?

I’m trying to get a sense of how much energy a 27 horsepower engine outputs. 27 hp $=$ 20 133 watts (joules/second). Potential energy can be calculated as $E = mgh$ where $g = ~9.8\ m/s^2$ on earth. ...
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Why is potential energy negative when orbiting in a gravitational field?

I had to do a problem, and part of it was to find the mechanical energy of satellite orbiting around mars, and I had all of the information I needed. I thought the total mechanical energy would be the ...
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2answers
2k views

How does the energy in a standing wave travel beyond a node?

In a standing wave, how does energy travel past a node? It should just get reflected. Assume the case of first overtone and you strike the string at a place. How will energy distribute itself? If it ...
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1answer
147 views

Total energy is extremal for the static solutions of equation of motions

In physics total energy is extremal for the static solutions of equation of motions. Can anyone explain this sentence to me?
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1answer
274 views

The relation between Hamiltonian and Energy

I know Hamiltonian can be energy and be a constant of motion if and only if: Lagrangian be time-independent, potential be independent of velocity, coordinate be time independent. Otherwise ...
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4answers
3k views

Which is more efficient, heating water in microwave or electric stove?

So our propane tank in the kitchen ran out again today. Which is more energy efficient, boiling water in a microwave on an electric stove? All things being equal i.e. starting temperature and mass ...
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7answers
368 views

My math says this is wrong, but what part of energy conservation am I violating?

Basically energy of conservation says it doesn't matter what path I take, energy will be the same from before as it is after. So I took the block at the top's energy equal to the energy when it ...
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2answers
2k views

How do electron configuration microstates map to term symbols?

I am trying to understand energy levels of electron configurations. I visited the NIST web site and discovered that the notation used here are called term symbols. After reading corresponding ...
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1answer
37 views

Joules To Move A Kilogram In Space [closed]

If roughly ten joules lifts one kg on earth one meter, how many in space? Meter / joule/kilogram Kilogram/meter/joule
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3answers
103 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
109 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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1answer
74 views

Work-Energy-Power Relations

A wind-powered generator converts wind energy into electrical energy. Assume that the generator converts a fixed fraction of the wind energy intercepted by its blades into electrical energy. ...
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2answers
154 views

Derivation of rest energy in Landau & Lifshitz

In Landau & Lifshitz The Classical Theory Of Fields there's a statement: $$\mathscr E=\frac{mc^2}{\sqrt{1-\frac{v^2}{c^2}}}\tag{9.4}$$ This very important formula shows, in particular, that ...
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293 views

Elastic potential energy of compressed spring? [duplicate]

If a compressed spring is dissolved in acid what happens to the elastic potential energy of the spring?
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3answers
1k views

Can antimatter be used as fuel for nuclear reactors?

I completely understand the difficulties of making and storing antimatter, so I am not talking about the mechanism or the way of doing it here, I am just talking about the concept. As far as I know, ...
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2answers
82 views

Is energy simple or composite?

From $E=mc^2$ it seems mass and energy are interchangeable. I can understand that mass is distinguishable, one type from another, such as protons and electrons. But in the reverse process, how is it ...
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2answers
275 views

Negative potential energy of gravity

Does the negative potential energy in the gravitational field have to be considered in calculating the total mass of the system in question (because of $E=mc^2$)? If so it seems to me that the ...
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1answer
134 views

Maximum separation when 2 unlike charges shot apart

I want to compute the maximum separation when 2 unlike charges are shot apart from each other ...
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1answer
95 views

Locally every force admits a potential?

I have a little doubt about a force being or not conservative. Well, as I understood, some forces cannot be expressed as exterior derivative of some scalar potential because the work done by the force ...
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1answer
240 views

How to guarantee that a kilogram of antimatter will quickly annihilate another kilogram of matter?

What I mean is, suppose we could somehow get a kilogram of matter and contain it safely. Now lets say we want to make a bomb using this kilogram, now, we have two ways, either store another kilogram ...
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1answer
894 views

Explanation of energy levels in molecules, atoms, nuclei and their relationship

Why are the energy levels of molecules, the atoms that form them and the nuclei inside the atoms considered separately? Or phrased in a different way- what is it that makes their energy levels so ...
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1answer
5k views

Needed Energy For Lifting 200 kg weight

I'd like to learn how much energy I need to lift a 200 kilograms weight on normal earth conditions? For example how much electric power do we need? I'm not a physicist and not a student and this ...
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1answer
98 views

Neutrino beam energy

Neutrino is one of the most mysterious particles in todays physics. Even when values of some parameters like for example mass associated with it are not known (or there is great range of possible ...
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2answers
1k views

Extracting heat energy from a material

Does it violate any physical laws to take a portion of the energy out of a system and use it? Specifically I'm referring to heat. (Kinetic energy). For example, if you have a material which has a lot ...
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0answers
31 views

Temperature dependence for specific thermal diffusivity in the diffusion formula

I recently found this answer about the diffusion equation (nice one actually), but have one doubt about the temperature dependence of this formula. If the "packet" of energy (terminology suggested ...
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1answer
40 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
93 views

Escape velocity problem

I was given a problem at school: How much Energy do we need to make a rocket of mass $m$ faster than the escape velocity so that it can travel in outer space? Here's how I worked: I know that ...
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2answers
81 views

Perspective and changes in kinetic energy

Say you have two planes flying next to each other at the same speed and one decides to pick up speed by burning a tank of rocket fuel. If someone on the ground wanted to know that plane's new speed ...
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2answers
118 views

Creating Energy!

I have this doubt in my mind for a long time, see if we rotate a fan in space: it would keep on rotating forever and would never stop. Due to no air friction present in space. I could never really ...
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2answers
207 views

Does our existence cost us energy?

Anything when it needs to inform its presense such as electromagnetic presense of charged particles and gravitational presense of particles due to their mass does so by sending information of its ...
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3answers
1k views

Does light loses its energy when it passes through denser medium

I know it does not because it emerges out of denser medium at 300,000 KM per second, but according to E=MC square and given that speed of light decreases inside denser medium with refractive index ...
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3answers
2k views

Work, Energy & Power - Body slides down a hemisphere

A small body of mass $m$ slides down from the top of a hemisphere of radius $r$. There is no friction between the surface of the block and the hemisphere. The height at which the body loses contact ...
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1answer
219 views

does matter radiate energy? [duplicate]

Since we know that all accelerated charges radiate energy and we also know that all matter is made up of protons and electrons which are all the while doing accelerated motion.So from this can i ...
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45 views

Bass and Treble-Car Steroes

In a car which phenomenon, diffraction or the resonant frequency of the car, lends itself more to the ability of bass to go farther? Related Answer: Why do bass tones travel through walls?
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1answer
345 views

Composition of solar spectrum

I read some where that there are three types of UV and infrared rays namely UV-A, UV-B, UV-C and near infrared, mid infrared and far infrared. Which is the most abundant among the the three in ...
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2answers
405 views

Does the potential energy related to a particle determines its rest mass?

Would it be possible to determine the rest mass of a particle by computing the potential energy related to the presence (existence) of the particle, if this potential energy could be determined ...
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2answers
848 views

How did the inflaton field “add” energy to the universe?

How did inflation add energy to the universe? What mechanism did this occur by? In other words, where did that energy come from? Was it due to the quantum fluctuation (or that scalar field rolling ...
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1answer
252 views

Tubelights+power lines pictures?

I've come across many pictures like these, sometimes in chain emails reporting the dangers of power lines. Another claim is that they run on "wasted" energy. The explanations given are that the ...
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2answers
382 views

Calculate the electric potential energy stored in a capacitor [closed]

Calculate the electric potential energy stored in a capacitor that stores 3.40 x 10^-10 C of charge at 20.0v I am lost. I am scared.
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2answers
561 views

How we can find the kinetic energy? [closed]

A solid disk of mass m is rolling along a surface its center has velocity v what is the kinetic energy of disk?I cannot solve the problem,
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2answers
192 views

Show that the energy levels of a particle in a specific potential are $E_n=(n+\frac{1}{2})h\omega-\frac{1}{2}\frac{F^2}{m\omega^2}$ [closed]

A particle of mass m moves on the x-axis under the influence of the potential $$V(x)=\frac{1}{2}m\omega^2x^2+Fx$$ Can anyone help me, using Schrödinger's equation in one dimension that the energy ...
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2answers
416 views

Energy source of electrons?

I am aware that electrons are moving in an empty space so basically there is no friction to slow it down and its velocity stays the same. However where did the electron get its energy from in the ...
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1answer
44 views

About how much force would something have to exert to be effectively unstoppable? [closed]

Assuming an object is moving in a straight line propelled by a force. How much energy would that force have to exert so that there are no known forces or objects that could stop it from moving in that ...