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

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Electric potential energy and signs

I know that eletric potenial is negative near a negative charge and positve near a positive charge. But does this mean a small positive 'test' charge has a negative electric potential energy near a ...
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24 views

Calculating power [on hold]

I need some help and explanation with solving this question: What is the power required to give a body of mass m a forward acceleration of a when it is moving with velocity v up a frictionless ...
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1answer
8 views

Thermal resistance of thermal interface materials?

Thermal conductivity are often used for surfaces between the computer chip and the heat sink to increase heat transfer and they want high thermal conductivity to decrease the thermal resistance. By ...
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1answer
30 views

The Energy involved in the work done here?

When a wire that has current $I$ flowing within it and its in a magnetic field, the wire experience the Lorentz force, and that force moved the wire over a certain distance $x$(no matter how small), ...
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27 views

What does it mean for a subatomic particle to “have” energy?

From my limited classical interpretation of the universe, i've always found it convenient to think of energy as what happens when an object isnt in its equilibrium position in the universe, and thus ...
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34 views

Particle in a 2D box degeneracy [on hold]

I'm doing revision for my quantum test next week and my university, irritatingly, doesn't provide mark schemes to past questions. I feel like I've done most of this one right, but the end has thrown ...
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1answer
28 views

Keep an object at a certain hight, does it require energy? [duplicate]

If i have an object with a defined mass, like a stone, and put it on the shelf it will sit there forever (lets forget all external influences). But if I have to hold up the stone I will eventually ...
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2answers
31 views

water pressure in the oceans or great lakes

Is there a way to create energy from water depth pressure? Convert the pressure to any type of energy? Does there need to be movement? Can someone comment on this process? Thanks
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Solving oscillation-related problems using energy [on hold]

I am very much interested in how exactly can one solve harmonic oscillation-problems using solely the KE - PE approach. I am a high-school student, so a little in-depth explanation will very much be ...
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16 views

Director field fluctuations in a liquid crystal in a magnetic field

If we consider the Frank elastic free energy in the equal constants limit (for more details, see here Chapter 4.1.) with an external magnetic field, we have $$ F = \frac{1}{2}\int \text{d}^3 r\left ( ...
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1answer
33 views

Is “atmospheric geostationary satellite” feasible with current technology?

Meaning by "atmospheric geostationary satellite" a vehicle capable of hovering 30 km above Earth surface, hence insde atmosphere, for unlimited time, making use of air propellers, solar panels and ...
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1answer
40 views

How do I describe and calculate the effect of an impacting object?

My lab studies the physiology of impact injury on biological tissues. I use a pneumatic cylinder to impart injury into a biological sample and then assess the molecular and physiological changes in ...
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0answers
19 views

total amount of energy in the universe [duplicate]

What is the total amount of energy in the universe? is there the same amount of energy as negative energy, cancelling each other out? Or is it something different?
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1answer
36 views

Gravity force and dark energy [duplicate]

If gravity is a fundamental force which bends spacetime and dark energy is energy which stretches spacetime, what is the difference between the terms force and energy?
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44 views

Does non-matter energy curve spacetime? [duplicate]

I know that matter (mass) curves spacetime, but do other forms of energy do the same? I.e. is matter the only form of energy that curves spacetime?
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1answer
22 views

negative energy cancelling energy

In what circumstances can negative energy cancel out energy? If a positron and electron are created they cancel out as one of them has negative energy. Are there any other ways that negative energy ...
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2answers
72 views

If energy can neither be created nor be destroyed,what is the ultimate source of energy?

We usually say that the ultimate source of energy for earth is the Sun. So this means that sun creates energy but according to the law of the conservation of energy energy can neither be created nor ...
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45 views

How much energy would you need to halt Earth's spin?

I was curious about the feasibility of stopping the Earth from spinning. A way to start I suppose is by getting an idea of the theoretical energy requirements.
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2answers
54 views

If 'pure energy' is photons, and energy is conserved, how can matter and antimatter (electrons and positrons) annihilate into photons and vice-versa? [duplicate]

The first law of thermodynamics says energy cannot be created or destroyed. But we can collide photons to form electrons and positrons. Does this means that law does not apply in these microscopic ...
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1answer
36 views

Work done (by gravity) on paired blocks [closed]

Why does gravity do more work on the block going down? The total work done (by gravity) on the $8kg$ block is more than the work done (by gravity) on the lighter block. How?
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4answers
2k views

Free energy device - QEG. Is this for real?

I'm not a physicist but I ran across reports on the web of a so called over unity or free energy device that has been created that supposedly works. It's called the QEG. Does this seem legit or is it ...
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2answers
36 views

How will a particle with energy less than $V_{\rm min}$ behave?

Consider e.g. the finite square well: $V = -V_o$ between $x=-a$ and $x=a$, $V=0$ elsewhere Now for scattering states, $E$ must be $> 0$. For normalizable bound states, $E$ must be $< 0$ and ...
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2answers
250 views

Travel at the speed of light

Is it me who have a poor understanding, or does all matter have to become 'pure energy' in order to achieve speed-of-light speed? If so, does that mean that no material can achieve the speed of ...
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41 views

Mean energy harmonic oscillator

I know that for a particle under the potential $$V(x,y,z)=\frac{k}{2}(x^2+y^2+z^2)$$ the equipartition theorem says that it contributes to the mean energy to $\frac{3k_BT}{2} $ (one half for each ...
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1answer
66 views

How much computer power would we need to model every physical aspect of the universe [closed]

So I know there are equations that give you the total energy in the Universe(Friedman). So about if we we to simulate every single interaction from neurons to physical forces, strong and weak, ...
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1answer
65 views

How does negative energy from Hawking Radiation cause a Black Hole to shrink? [duplicate]

Hello this is expanding upon a question that was previously asked on stack exchange that I linked below. From what I understand of Black Holes is that overtime Hawking Radiation results in the Black ...
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4answers
45 views

Relation between Force, Time, and Energy

Is energy involved independent of force applied over time? In other words, if I wish to apply a force for much more time would I require more energy?
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3answers
33 views

Energy, time and force

Consider force $F$ acting on a body of mass 1000kg and the displacement be $s$. So energy required to do so is $F$x $s$. Now consider the same force causing same displacement on body of mass 1kg. ...
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2answers
38 views

The context of definition of work [duplicate]

It is unclear whether the work is defined considering opposite force on the same body or in ideal case where there is a single force acting on a body.If we consider ideal case where only a single ...
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1answer
72 views

Is magnetic wheel possible?

I once tried to make a magnetic wheel using different shaped magnets and placing them in different orientations and of different shapes.But it did rotate making a small angle ie it didnt rotate even a ...
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2answers
41 views

Query into the cumulative velocity of mounted platforms

Consider throwing a stone at an object from rest, it travels at Vms-1. Now throw that stone whilst running at Ums-1. It seems in the latter scenario the total speed of stone is V + U. Now imagine ...
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1answer
32 views

Can a laser be designed to ionize muons so as to prevent a-sticking?

Muon catalyzed fusion is currently little more than a lab curiosity today in part because of how many hydrogen nuclei can be fused before the muon is carried away by an alpha particle. ...
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1answer
47 views

What is Work? What does the quantity suggest intuitively? [duplicate]

The mathematical formula for work says that work is force into displacement, but what is the philosophy behind it? I mean what does the quantity suggest?
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1answer
39 views

How did Lyman discover his series?

How did Lyman discover his series in hydrogen atom? How did he know that the final energy level is the first level and not the second or the third or etc.? Or how did the other scientists know which ...
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4answers
41 views

Optimizing water boiling

I'm about to prepare some spaghettis and to do so I need 2 liter of boiling water. For getting the water to certain temperature (lets say 100 Celsius degrees) from a starting temperature of 15 ...
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2answers
69 views

Potential energy of an infinitesimal length of elastic rod

I am having an embarrassingly hard time with the derivation for the potential energy of an infinitesimal element of an elastic rod of area A. The picture shown below is an element of the rod that has ...
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0answers
17 views

Am I understanding power correctly? [duplicate]

4 men weighing 380kg, carrying a 380kg piano up 5 meters will generate 31 watt if the load takes 20 minutes. Now this is very hard to do and saps the strength out of any human being. However, that ...
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1answer
21 views

Excited Energy levels of Hydrogen vs Solids

My question has to do with Excited Energy Levels. I keep reading and learning that all objects/most solids emit infrared radiation. But to emit radiation, an object's particles must first enter a ...
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4answers
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Can one obtain free energy from the vacuum?

It is known that from the vacuum of a quantum field theory, virtual particle pairs are created and destroyed; is it possible to capture these particles thus obtaining free energy from the vacuum?
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2answers
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Do there exist objects that absorb energy only (and do not give it away)?

Do there exist objects that absorb energy only (and do not give it away)? Magnets have been mentioned in this post, do we know more examples? Extract energy from magnets And how is this capability of ...
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1answer
40 views

Could there be massive gravitons and in our spacetime? [closed]

My question is: Could there in principle be sub-groups of gravitons (if they existed) that has mass (and in our spacetime dimensions) such as those affected by electric or by strong force or other ...
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0answers
19 views

What is Fermi energy and Fermi level? [duplicate]

What is meant by Fermi level and Fermi energy? And what is the difference between the two?
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1answer
78 views

The relation between the movement of electrons and energy

So, I've been enjoying reading a lot of helpful posts, but now, I found myself in the need of asking something. I have a hard time grasping the general concept of electricity / how the relation ...
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1answer
22 views

Energy Stored in a Capacitor with and without Dielectric

I have seen the equation $V = \frac {V_0}{K}$, but also the equation $V=\frac{1}{2}CV^2$. The values of C and V increase in the same linear ration with K (because $C=KC_0$). However, as the energy ...
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3answers
560 views

What happens to gravity after matter-antimatter annihilation?

Both matter and antimatter have mass and thus gravity, but since energy from annihilation has no mass what happens to the force of gravity that was previously present? What about conservation of ...
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1answer
56 views

How does someone move space?

I've heard that we've known components of the universe appear to be flying apart faster than $c$, and that this can happen because the space containing these materials are also moving apart. How does ...
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3answers
1k views

Reducing the Tsunami impact using Nuclear bombs [duplicate]

I am a novice on this topic. However, I wonder if we use nuclear bombs against the tsunami, will it reduce the speed and impact of the tsunami. Is it possible to break the massive wall of waves using ...
4
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1answer
65 views

Kinetic energy question

Thought experiment: I am starting to walk on a coridor... From the coridor's perspective I have a certain increase of kinetic energy. From my perspective the whole universe is gaining kinetic energy ...
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2answers
467 views

What's this about kinetic energy increasing with the fifth power of length?

I don't quite understand this quote from Stephen J. Gould's Ever since Darwin, where he talks about the compensating physical characteristics of organisms for their size. Other essential features ...
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2answers
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Total energy of a quantum gas

I'm dealing with a quantum gas, thought as a system of N non-interacting particles. I would be tempted to say that the total energy of the system equals the sum of the energies of the single ...