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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0answers
27 views

If energy is relative, mustn't conservation of energy be a silly thing [on hold]

If velocity is relative then kinetic energy is relative then the total energy is relative. And the law of conservation of energy must be wrong because it is way not fundamental otherwise it would work ...
0
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0answers
30 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 ...
2
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1answer
53 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
21 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 ...
-1
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1answer
16 views

Explanation to; Energy loss from a vertically bouncing mass on a spring [on hold]

Basically i have been assigned this title in my physics coursework of the (IB) and im struggling to get started. I have read my way through the internet, with ought any success. I hope one of you ...
2
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3answers
53 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?
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1answer
39 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 ...
2
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0answers
43 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?
2
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1answer
40 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 ...
0
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1answer
33 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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0answers
24 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.
1
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1answer
23 views

Evaporate water using compressed air [on hold]

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 ...
4
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1answer
41 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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2answers
76 views

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

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 ...
2
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4answers
208 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 ...
0
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1answer
33 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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1answer
34 views
+50

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 ...
1
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1answer
32 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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4answers
123 views

How to derive $E=mc^{2}$

Is there some way to derive $E=mc^{2}$? I can understand that energy in something is proportional to its mass, but the $c^{2}$ part... I have no idea. It seems like the way the units are going it ...
0
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2answers
67 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 ...
0
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0answers
15 views

Drawbacks of passive energy utilization [closed]

Solar plants utilize free energy coming from the Sun. Is that possible that on some significant levels of solar energy utilization we may encounter a negative side effect? Cause energy will avoid from ...
3
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2answers
51 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 $\mu$?
2
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0answers
49 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
26 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 ...
0
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1answer
80 views

Why is there zero point energy at absolute zero temperature? [closed]

If we define the absolute zero as a temperature which there is no entropy in it so why should we have zero point energy?
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0answers
21 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 ...
3
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1answer
40 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
51 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 ...
0
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1answer
27 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 ...
1
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1answer
55 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
412 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
77 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 ...
1
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3answers
67 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, ...
3
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2answers
56 views

What would happen to a star if a Dyson sphere lined with mirrors reflected a significant portion of the stars light back to the star

I have looked for similar questions here on stack exchange. The closest example to this that I found is Could a Dyson sphere destroy a star. That question assumed less than perfect absorption of ...
2
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0answers
36 views

Particle moving under force $F=-cx^3$ [closed]

A particle with mass $m$ moves under influence of a force $F=-cx^3$, with $c$ a constant. What is the potential energy function $V(x)$? And if it starts to move from rest from position $x=-a$, what ...
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1answer
34 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 ...
2
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2answers
53 views

Car motor heat to drive a steam engine

Why wouldn't be able to place a car motor inside a water tank or another liquid to be heated by the motor, instead of wasting the heat and then use the steam generated, to drive a steam engine, which ...
0
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1answer
45 views

Does gravity (and all other fundamental forces, for that matter) have infinite energy as they seemingly last forever? [duplicate]

If I put a brick onto an steel platform, that platform can hold the brick A LONG TIME, if not FOREVER. Does the platform exert force? If so, then shouldn't it have infinite energy to resist the pull ...
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1answer
20 views

Polarized Filtering Frequency Shift?

A polarized filter is exposed to a unpolarized light source. The output of the filter should be of lower intensity, hence lower energy. Should not the filtered light be of a lower frequency to ...
0
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2answers
26 views

How does matter get the energy to repel the gravitational effects of itself to to other matter

This has always puzzled me. As i stand on the earth i require energy to exert a force over gravity to enable me to keep standing. The net force between me and the the earth is zero and thus i remain ...
0
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2answers
31 views

Calculate required power output for a laser

How to calculate power rating required for a laser in order to produce a dot at a specific distance after reflection? For example, the laser is 10cm from the mirror, at an angel of 30 degrees it ...
4
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4answers
82 views

Different kinds of energies in the form of $\frac{a_1a_2^2}{2}$

It seems to me that the energy of some kind frequently takes the form $$\frac{a_1a_2^2}{2}$$ Where $a_1$ and $a_2$ are some variables. So, for example, kinetic energy has $m$ and $v$; rotational ...
0
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4answers
116 views

Why aren't we affected by radium?

1)We have radium clocks, watches, wrist bands and many things which glow because of radium but we know that radium is radioactive so why isn't it harmfull for us when in bands, watches etc. 2)Does it ...
0
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3answers
38 views

When moving from one position to another at a constant velocity, how does the conservation of energy hold?

I know that this might be a duplicate question, but I have not found any satisfactory answers that clear up my lack of understanding. Here is my question. Say a sloth hangs on a tree in the middle of ...
2
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1answer
41 views

Can the Cosmic Neutrino Background be detected from a lab moving near the speed of light?

If I've understood it correctly, the energy of an object depends on the reference frame, so when you accelerate, the CMB and CNB appear to gain energy (relative to your rest frame). So if you are ...
0
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1answer
38 views

Can a solar panel work with heat?

As we know that a solar panels due to the energy of light, but can we run a solar panel with the same amount of energy provided as heat?
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2answers
32 views

What theories or formulas are involved with velocity

What theories or formulas are involved or can be added as background information in an experiment that sees a small toy car roll freely down an incline where the surface area is altered to cause more ...
2
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2answers
66 views

Lack of rigour in usual derivation of Work-Energy Theorem

The derivation of the Work-Energy theorem usually goes as follows: You define the work done on a particle under net force $\vec{F}$ as $$W=\int\limits_C \vec{F}\cdot\mathrm{d}\vec{r}$$ And then you ...
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3answers
36 views

Work and energy

when a ball of mass m is brought with uniform velocity from infinity into the g field of the earth at a distance r from it, the potential energy of the ball earth system decreases from 0 to -GMm/r. ...