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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103 views

What really happen with resonance inductive coupling

I can't figure out the picture of resonance inductive coupling I can image how magnetic inductive coupling works, It scatter magnetic around one coil and if second coil being near it then induce ...
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0answers
32 views

Energy density question

I have looked for these formulas everywhere but cant seem to find them... What is the formula for the energy density of the electric current ,and the energy density of the mechanical wave?
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1answer
34 views

Deriving pressure from a given partition function

If the partition function for some system is given as $e^{\text{$\alpha $T}^3V}$; please note note that $\alpha$ is a constant. I have computed $$\left[\frac{\text{$\delta $Z}}{\text{$\delta ...
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1answer
215 views

Is it possible to harness energy from the exothermic reaction of changes of state of matter?

Since a substance emits heat as it transitions from a high energy state (gas) to a lower energy state (solid), is it possible to devise a method to capture this heat and convert it to usable energy? ...
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1answer
364 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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0answers
35 views

Calculating the energy of a string wave with different phase and group velocity/amplitude/etc

(Please note this is mostly a theoretical, mathematical question, not one about specific particles. Let me know if this is more appropriate in Mathematica) The energy per wavelength of an ideal ...
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1answer
143 views

What happens to gas molecules after ionization?

I know that gas molecules conduct electricity after they get ionized but what will happen if we keep increasing the voltage even after ionization? Will it explode? If it will then how much energy ...
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0answers
18 views

Dipoles and Potential Energy

I was pondering about electrostatics, particularly dipoles. How would one go about calculating the difference in potential energy of a dipole an arbitrary distance away from an arrangement of another ...
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2answers
102 views

Is it feasible to transfer energy from power stations to communities via photons instead of electrons?

Electrical wires are relatively inefficient in transferring energy--especially when the place of production is quite far from communities. Would it be possible to transfer that energy via photons? I ...
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3answers
45 views

What triggers a nuclear chain reaction?

A nuclear fission works by spliting atom's neutrons by neutrons which release energy but how is the chain reaction triggered because at first the nucleus is bond by a strong nuclear force so what ...
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0answers
33 views

Creation of energy [duplicate]

When I'm learning about energy. There is a sentence leave me hang. Energy cannot be created nor be destroyed So, if energy cannot be created, so how can we have energy in this world in the first ...
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1answer
242 views

Why potential energy of external force on particle attached to spring is equal to full force multiplied by full displacement?

I am having quite difficult time to understand the meaning of total potential energy on spring. All references I read say that the total potential energy on particle attached to spring is: ...
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1answer
79 views

2nd law of thermodynamics - thought experiment

I have designed this simple thought experiment that seems to contradict 2nd law of thermodynamics. Could you please find a mistake in my reasoning? ...
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1answer
23 views

Relative Movements Agreement on Object speed

I am confused about Relative Motion.Lets suppose we have one train and two observer.One of them inside the train and the other one is outside.Lets think the outside observer see the train moves a ...
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0answers
4 views

Vertical wall at 3 different temperatures - do the same natural convection coefficient correlations apply?

I have an vertical enclosure that consists of 3 shelves, each with its own temperature and are thermally isolated from each other. We will call the shelves A, B, and C with A being the base shelf. The ...
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3answers
69 views

Kinetic energy and Potential of a photon

How does the potential and kinetic energy of a photon relate? Do they mean the same thing? Also how does De broglie wavelength and Potential relate?
2
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1answer
45 views

How can I set up an equation for distance traveled for a rubber band powered car?

I am to make a rubber band powered car, and I have to maximize it's distance traveled. The time taken to reach said distance, top speed of the car, acceleration of the car, is not relevant. I just ...
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1answer
45 views

Graph of energy stored in capacitor?

Question: In an experiment a capacitor is discharged through a constant current. Draw a graph of how the energy stored in the capacitor varies with time. The answer given is: But I seemed to get a ...
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0answers
49 views

Is refraction of light a thermodynamic process?

Is refraction of light a thermodynamic process? Can it be explained by conservation of energy? If so, does temperature has an effect on refraction of light?
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2answers
392 views

If conservation of energy was wrong, how would we know about it?

Suppose you just started learning physics and you've been introduced to conservation of energy and kinetic energy. Apart from those concepts you know next to nothing. Then you observe an inelastic ...
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2answers
61 views

What observations would be needed to falsify the law of conservation of energy? [duplicate]

I've been doing some thinking, and began to wonder: What observations have led us to the conclusion that ‘energy can neither be created nor destroyed’? Essentially, this means that the big bang ...
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1answer
37 views

If an electron tunnels and loses amplitude, but maintains energy; where does the rest of the amplitude go?

I'm assuming the 'amplitude' is kind of like the MeV it has on it, so could be seen as a product of the voltage applied to that electron in a field. But how can it 'lose' volts when passing the ...
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6answers
756 views

Why is momentum conserved (or rather what makes an object carry on moving infinitely)?

I know this is an incredibly simple question, but I am trying to find a very simple explanation to this other than the simple logic that energy is conserved when two items impact and bounce off each ...
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0answers
25 views

Why does kinetic energy quadruple when speed doubles? [duplicate]

Why does kinetic energy quadruple when speed doubles? Please explain (in simple terms) with examples if possible.
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1answer
40 views

Evaporate water using compressed air [closed]

I want to evaporate water by forming air bubbles which are formed by flow of compresses air through perforations. What is the energy (in KWh) input to compress 1 cubic meter volume of atmospheric ...
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1answer
45 views

Optimal size for a bike tire

While I was riding my bike funnily enough I wondered if there was an optimal size for a bike wheel. So I suppose that is my question, What is the optimal size for a bike wheel? If the bike accelarates ...
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4answers
1k views

Are there any theoretical limits on the energy of a photon?

Is there any lower or upper limit on the energy of a photon? i.e. does the mathematical framework we currently use for Quantum Mechanics blow up when a photon surpasses a certain upper limit of ...
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4answers
219 views

If a bell is rung in a perfect vacuum and is suspended by opposing magnets will it ever stop ringing?

As far as I am aware a bell rung in a perfect vacuum would only lose energy and stop ringing due to friction between the bell and the hanging mechanism (due to the lack of air resistance). Therefore ...
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1answer
94 views

Work functions of ceramics/insulators

Is anyone aware of or know of a good source or means of estimating the work function of a ceramic material? Typically, work functions are given for pure elemental metals, rather than for compounds, ...
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2answers
79 views

A different interpretation of $E=mc^2$ but no idea what it might mean [closed]

I wanted $E=mc^2$ to look like an 'inverse square' sort of a formula. So this is what I derived: $E=mc^2$, so; $m=E/c^2$, assuming $E=E_1E_2$ (I am aware that when you decompose energy into two ...
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1answer
41 views

Does a closed system with fixed entropy imply an isolated system?

Just first to clarify, my university notation is $$\text{change in entropy} = \text{entropy flow} + \text{internal production of entropy}$$ I am confused with the term fixed entropy. Does that mean ...
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2answers
71 views

can kinetic energy be independent of mass.?

Why is it said that the kinetic energy acquired by a body of after traveling a fixed distance from rest under the action of constant force is independent of mass? Nd yeah the mass of the body is ...
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1answer
37 views

How to determine if a potential admits bound states?

According to Griffith's Quantum Mechanics, "$E$ must exceed the minimum value of $V(x)$, for every normalizable solution to the time independent Schroedinger equation" As an example, there is no ...
3
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2answers
58 views

What is precisely the energy scale of a process?

Coupling constants run with the energy scale $\mu$. But what is exactly this energy scale. My question is, if I have a physical process, how do I compute $\mu$?
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0answers
51 views

How to relate internal energy to atomic motion?

I am trying to conceptualize how atomic motion leads to the thermodynamically-defined internal energy (denoted as $U$ below) through some broad mathematical relationships. I get that the internal ...
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0answers
27 views

How complex is an energy balance for this problem?

Let's say I have an enclosed room in the shape of a box with forced airflow on the outer walls at an ambient temperature. Each end of the room (forward and rear) has a vent that ducts in warm air to ...
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1answer
93 views

Is it possible to calculate the energy of a spark?

I am not a physicist, but this question came to me and I need to answer it, and I think that you guys can help me. Actually my question is just like in the title. Is it possible to calculate the ...
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0answers
24 views

What is the connection between Bragg's condition with reduced EK diagram?

In my course notes the professor mentioned that there was some relationship between the Bragg's condition and the first Bernoulli zone of the reduced EK diagram. Specifically, the boundary before ...
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9answers
3k views

Does it take more energy to open a door when applying force close to the hinge?

Assuming an ordinary hinged door (without any springs), would it take more energy to open it when applying force in the middle of the door (point b), rather than at the end of the door (point a), ...
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1answer
42 views

Why is energy in a system typically able to be described using quadratic expressions?

This might be more of an applied math question. Why is the energy of a system typically able to be described using quadratic expressions. Is there an underlying mechanic that drives this?
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1answer
54 views

Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy? [duplicate]

I want to know the configuration where the system would be most stable.I only know basic Physics & Maths and cannot start solving the problem.I can understand it for 4 charges and 6 charges as a ...
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1answer
28 views

Is it possible to make use of the gluon field's energy to use is applications?

As we know most of the mass of the proton comes from the energy caused due to the interactions of the quarks with the gluon fields (reference link of this statement ...
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2answers
2k views

Finding maximum speed in a work-energy problem [closed]

I have the following problem: The Royal Gorge bridge over the Arkansas River is $310\text{ m}$ above the river. A $57\text{ kg}$ bungee jumper has an elastic cord with an unstressed length of ...
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1answer
61 views

Do Waves have mass? [duplicate]

Do any form of electromagnetic waves like visible light have mass? It is known that all electromagnetic waves have energy. According to Einstein's $$ E^2=p^2c^2 + m^2c^4 $$ formula, the energy of a ...
3
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4answers
423 views

Is it possible to generate energy by the moon orbit?

My question could be a little bit surreal, but I was thinking about this: A hydroeletric plant transform the energy from the water passing through the turbines into electricity. Correct? If the ...
2
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1answer
80 views

Massless particle that have momentum not equal to 0

I saw some problems in special relativity that use conservation of total energy and momentum and the conclusions are spectacular. My problem is the following: how can a massless particle like neutrino ...
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4answers
7k views

How do you determine the heat transfer from a P-V diagram?

I doubt this question has been addressed properly before, but if there are similar answers, do direct them to me. I am currently studying the First Law of Thermodynamics, which includes the p-V ...
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3answers
72 views

Work-Energy conservation with friction

I didn't go to the lesson of work-energy theorem, so I miss something about this subject. I know the formulas, but I can't figure it out. This question has many quantities. Here is the problem, ...
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2answers
232 views

$E=kT$ or $\frac32kT$?

Basically, which is the correct formula for thermal energy, and is this the same as kinetic energy? My notes are pretty conflicting on this topic, and I'm getting pretty confused.
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1answer
36 views

How do you define the total rotational energy of an object?

This problem arose when I was applying a conservation of energy argument to a mechanics problem, (a spinning coin on a table) and wasn't sure how to define the total rotational energy of the coin. At ...