# Tag Info

## New answers tagged energy

0

For the turbocharged engine, the first stage of the turbocharger causes a significant increase in the inlet air temperature as the air is compressed. The temperature increase leads to a larger volume of air than what would be expected if the air remained at ambient temperature, based on the ideal gas law. To avoid designing a large second stage on the ...

1

In addition to the other answer by Cort Ammon, I have heard of other psychophysical/evolutionary explanation: The frequency distribution of that sound closely corresponds to the frequency of a crying baby, which has been shown to drive people crazy when exposed to it for a short amount of time (we are genetically predisposed to get distressed by such a ...

0

I think you should look at Newton's 3rd law in a frame where forces are balanced and the initial impact transition has settled. e.g. when you hit the wall with 50 lbs force, even if you have good muscle control and apply close to 50 lbs to your hand, it does not move in a linear acceleration because it has to fight its way through a complex multi degree of ...

1

From http://www.livescience.com/16967-fingernails-chalkboard-painful.html: Interestingly, the most painful frequencies were not the highest or lowest, but instead were those that were between 2,000 and 4,000 Hz. The human ear is most sensitive to sounds that fall in this frequency range, said Michael Oehler, professor of media and music management at the ...

0

This has to do with energy efficiency. It does not have to much to do with the "density of oxygen" (the air density does not change significantly from $20^\circ\mathrm C$ to $0^\circ\mathrm C$. The reason is because $PV =nRT$ and $DV= {m}$ and $n\mathcal{M}=m$ rearrange to form: $$P= {DRT \over \mathcal{M}}$$ OR $${P\mathcal{M} \over RT}=D$$ And when ...

15

You've caught a non-intuitive part of Newton's 3rd law. It's actually applying in the case you mention, but because the objects involved are of dissimilar hardness it's easy to perceive the impact as a violation of the law. Impacts are actually really complicated. Consider this slow motion video of a punch to the gut. We won't be able to cover all of the ...

3

What makes you think that the maximum force you applied to the dry wall was anything like the maximum force you applied to the brick? It certainly wasn't. The dry wall gave way much before you were able to attain the same force as applied to the brick. Try punching the air and see how much force you are able to apply. The experimental evidence that the ...

0

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/imgnuk/bcurv.gif The answer to your question is contained in the curve linked above. Details: As can be seen from the binding energy curve, the binding (per nucleon) increases sharply as more nucleons are added at the lower mass numbers; it reaches a maximum at the Iron group (mass number near 56); and ...

5

TL;DR: The physics of hitting things are not as easy as exerting a constant force on something. What I am trying to say with that is that Newton's law of course applies, but it would be more obvious to see it if you were just pushing/leaning against the wall with your weight. Then I'd say the two walls probably feel roughly the same. So what is different ...

6

There is no doubt the Newton's third law holds in this situation. The source of confusion might the fact that you are neglecting the time interval of the collision so it is better to approach this problem by the momentum principle. The impulse of a force $F$ is given by $$I\equiv\int_{t_1}^{t_2} Fdt=\Delta p,$$ where $\Delta p$ is the momentum change due to ...

1

The more fundamental thing to understand are the conservation laws, particularly the conservation of momentum and of energy. The availability of energy gives rise to force. When you move your fist towards an object at a particular velocity you contain within it a kinetic energy and momentum. Materials are held together with binding forces that, at the ...

3

The time-independent Schrodinger equation $\hat{H} \psi = E \psi$ only holds when the Hamiltonian does not depend explicitly on time. If you start with a time-independent Hamiltonian and make a time-dependent gauge transformation, then the new Hamiltonian will depend explicitly on time, and there is no reason to expect that the (time-dependent) eigenvalues ...

1

If we measure length by a scale there is no change of energy. So it depends on subjects to be measured.

0

In LIGO and equivalents of course the mirrors or detectors can be considered to be moving and thus cause the change in the interference patterns, depicted as the waves we've seen graphical depictions (and sound) of. This movement is kinetic energy on mirrors or detectors, and so conceptually we get the electrical signals. These have energy, which came from ...

1

Interferometer "questions": clearly the mirrors can impart energy to the light and vice versa. But I think that a part of the answer is more fundamental than this: according to Feynman the passage of a detectable gravitational wave imparts energy to any coupled massy environment through which it passes, and indeed this is necessary for gravitational waves to ...

3

In a nutshell, no. Part of the problem seems to be that you misunderstand the fundamentals of string theory. The strings do vibrate. The frequency of these vibrations determines the type of particle and the energy of the string determines the energy of the particle. Second, your understanding of the uncertainty principle isn't quite right. Yes, we cannot ...

-1

To answer your primary question, from a physics standpoint: Dissolving sodium chloride in water ... has a free energy of -9.00 kJ/mol... The reverse process, separating sodium chloride out from water, requires the input of energy equal in magnitude to the free energy of mixing. Given seawater's average salinity of 35 ppt = 0.60 mol/L, and converting ...

2

Usually in engineering lingo, negative pressure means below-atmospheric pressure. If flue gases are at atmospheric pressure, then to make them flow towards the fan, the fan must create a negative pressure region at its inlet. Subsequently there is rise in pressure across the fan, going from inlet side to outlet side. Power supplied to fan is expended in ...

0

However, Robot A moves at a speed 9 times faster than Robot B. Are you stating this as a given, or do you presume it arises from the consequence of the gearing? If so, it is incorrect because an engine does not deliver a constant speed, but instead a maximum power. The higher geared robot will have a larger load on the engine, reducing the speed it can ...

0

In your question you have proposed the statement: space geometry is changed if and only if there is a kinetic energy difference between them. I need to tidy this up just a bit, so let's consider this related statement: the geometry of space-time is changed if and only if one observer is moving (or even better yet, accelerating) relative to the ...

0

If you consider a very diluted atomic gas with $N$ atoms (say hydrogen atoms), it won't be equivalent to an ideal gas with $3N$ degrees of freedom for all temperature ranges. Instead, at very low temperature but very low density, you will expect these atoms to form molecules e.g. $H_2$ molecules and the internal energy will be $5N k_B T/4$ as there are $5N/2$...

0

What do people actually mean by "rolling without slipping"? This question and the answer should give you better insight into your question. Think about the definition of rolling without slipping given and how friction is created and works for rolling objects maybe make a free-body diagram.

0

It depends on what you mean by "energy density". If you want to ascribe some energy to EM field in material medium in a general way, not requiring linear and lossless behaviour of the medium, the simplest way is to use the same Poynting theorem and formulae as in vacuum. Then density of EM energy is $$\frac{1}{2}\epsilon_0E^2 + \frac{1}{2\mu_0} B^2$$ and ...

-1

To expand on the above answer by @PhysLab (which is very well written), the answer depends on how "in depth" you want to look at it. Before discussing energy transfer, let's cover a few fundamentals, because these are slippery concepts and often misunderstood. (Including by me, so fingers crossed!) Let's look at what "energy" and its "transmission" involves....

2

Energy transfer can be thought to occur via the exchange of a 'virtual particle'. In nature, there are 4 fundamental forces, namely: 1. Electromagnetic force 2. Gravitational force 3. Strong force 4. Weak force Each of these forces have a different exchange particle: For instance, the exchange particle for EM is a photon whereas that for the strong force ...

7

There are two separate issues here (not sure which of the two you mean): The first problem is a severe misconception that is similar to Zeno's paradox of Achilles and the Tortoise: Given a hydrogen atom we have (in principle) an infinite number of shells. However, the gap between the shells gets smaller and smaller. If you would jump from shell to shell, ...

6

Update 1: 1) Note added in proof: The photon stress-energy densities obtained below more or less heuristically are identical to those obtained in more rigorous approaches from the electromagnetic stress-energy density tensor. 2) The physical reason why the stress-energy argument retrieves the detailed balance result in the OP, but is inequivalent to simply ...

3

The probable reason why poeple say ice cream heats up your body is when you compare the amount of heat that it takes away your body compared to the food caloric value of the ice-cream. 100 grams vanilla ice cream is about 207 food Calories ($207 kcal$) according to this site. On the other hand, the amount of heat that the ice cream takes from the body is ...

2

When the atoms get close to each other, the electrons of the first begin to feel the nuclei of the second, and vice versa. So, for example, when two hydrogen atoms approach each other, we have to consider the the potential due to all four particles (and the Pauli principle, but that issue doesn't have a bearing on the kernel of your question). The ...

-3

This problem is equivalent to Einstein's original thought experiment with the center of mass of a tubular spacecraft in an inertial reference frame emitting a photon from one end and reabsorbing it at the opposite end. This is the same thought experiment convinced an audience of Newtonian physicists that E=mc^2 by arguments related to center of mass. ...

0

In any harmonic oscillator, the period, acceleration and speed depend on the restoring force. In the vertical mass-on-a-spring, the restoring force is the net force on the mass, which is the difference between the tension in the spring and the force of gravity. The latter is constant, it does not vary with displacement, so the net force depends only on the ...

4

Let there be given a selfadjoint$^1$ operator $H^{(0)}$ and a (semi)positive operator $V\geq 0$ on a Hilbert space ${\cal H}$. Let the basis of normalized eigenvectors for $H^{(0)}$ be $(|i^{(0)}\rangle)_{i\in I}$ with corresponding eigenvalues $(E^{(0)}_i)_{i\in I}$ ordered such that  \forall i,j ~\in~I:\quad i~\leq~j\quad\Rightarrow \quad E^{(0)}_i~\leq~...

0

Consider a piston cylinder arrangement. Pressure * Area equals force and this force moves by a distance ds (consider piston moving upward by a distance ds) then work done = Fdx = PAreads =Pdv. Volume of cylinder equals Area *height

0

Q is heat and W is work. Q is considered positive when it is added to the system and work is considered positive when work is done by the system. Also remember that Q and W are energies in transit I.e energies associated when system moves from one state of equilibrium to another state of equilibrium. One cannot say that "Q" amount of heat is present in the ...

4

Do radio waves from the Sun reach Earth? Of course they do. It's just another form of electromagnetic radiation. If so, do they penetrate the atmosphere or are they reflected, absorbed, or scattered? That depends on frequency (or wavelength). The atmosphere reflects, absorbs, or scatters most incoming electromagnetic radiation. There's a window in ...

1

Offhand I'm not sure where to find information about how much is absorbed, reflected and scattered, but the waves certainly do reach Earth, and some, at least, penetrate the atmosphere and end up in solar radio observatory detectors, otherwise we wouldn't have so many of them.

2

Apples and oranges. The first is the photon density in a volume whose radiation field is in thermal equilibrium. The second is the rate at which photons pass a unit area regardless of the source of the radiation. They are both correct, but they describe different things. BTW, it's much better to tell us what is in a document instead of asking us to look ...

0

The equilibrium position for the vertical spring is different from the horizontal spring. The vertical spring is stretched by the weight of the mass. The elastic potential energy in the spring depends on its displacement from its unstretched length, not from the equilibrium position. The elastic potential energy is proportional the square of the ...

0

I'll answer your question in three parts. "What is the average range of voltage in sky?" I would hope that for sunny skies, it's near zero - otherwise it'd be nothing but bolts from the blue all day long. But I assume that you're talking about the average range of voltage in regular lightning. NOAA says that we have .1-1 billion volts in lightning. "I ...

2

Typical domestic electricity consumption is 3,300kWh per year, or about 64kWh per week. Gas consumption is 16,500kWh per year; if you do not have a gas supply, your total power consumption would be about 380kWh per week. The maximum current which can be drawn per house from the mains is 100A. This is set by a fuse installed by your supplier close to ...

1

Generically, the answer is "no". The Zeeman effect is the splitting of degenerate spectral lines in the presence of a static magnetic field. As the field strength increases, some lines move to higher energies and some lines move to lower energies. Example of the splitting of the $5s$ orbitals of Rubidium: (Graph created by: Danski14. Image used under ...

2

Consider $\tilde{V}(x)=V(x)+\Delta(x)$ where $\Delta(x)>0,\forall x$. Within 1st order perturbation, $E_n=E_n^0+\langle \psi_n|\Delta|\psi_n\rangle=E_n^0+\iint dx_1dx_2\psi_n^*(x_1)\delta(x_1-x_2)\Delta(x_2)\psi_n(x_2)=E_n^0+\int dx|\psi_n(x)|^2\Delta(x)>E_n^0$

7

You can show this by using perturbation theory (only for suitable small changes in the potential). When you assume, that $\tilde{V}(x) = V(x) + c$ with $c > 0$, then you can write your problem als perturbation: If the unperturbated hamiltonian $\hat{\mathrm H}$ has eigenstates $| \Psi_n \rangle$ with discrete energies, then perturbation-theory states ...

0

In general, electronic relaxation of an excited atom is nothing but a quantum mechanical transition from an initial to a final state. Therefore probabilities for different transitions (what you called paths) is determined by the rules of quantum mechanics. The particular "law" that applies here is called Fermi's Golden Rule. In the related Hyperphysics page ...

1

It is all question of scale. If we could harness tidal energy at large scale and more effectively it would slow down the earth faster but at the scales practical now it is not even comparable to topographic changes due to erosion of the continental shelves which brake the tides. Shifting of tectonic plates and mountain ranges could affect the balance of ...

19

Ultimately, the short answer is yes. The moon is slowly moving away from the Earth, at a rate of 4 centimeters per year. This is due to it being in a slightly higher orbit than equilibrium. At the same time, the Earth, being a satellite of the sun, is having its rotation rate slowed, until it will eventually be tidally locked with the sun. Both of ...

34

The moon does work on the Earth because the Moon orbits around the Earth at a different speed than the Earth's rotation. So, as time passes, different parts of the Earth feel the maximum strength of the Moon's pull, leading to oscillations in the height of the Earth's surface, which can be exploited for energy extraction. The Earth has always been ...

5

General wave functions can be expressed in terms of any set of eigenfunctions. But for bound systems, the energy eigenfunctions have a couple of appealing properties that make them popular: The energy eigenfunctions are the solutions to the time-independent problem, so you can work on a steady-state system. This often makes the math a lot easier. The ...

2

Can Light Really be Matter? I suppose it depends on what you mean by "be". Matter will be created from light within a year, claim scientists It just is counter-intuitive to me. This is the fallacy of reasoning from personal incredulity. It isn't a good guide. I find most of QM and relativity counter-intuitive - it doesn't seem to be a simple ...

0

Interesting question. Light isn't matter. Matter is generally described by fermions, light is described as a boson. These are different. Though they have qualities in common, for example energy or mass or spin. Interestingly, Heisenberg judged that energy was 'equivalent' to the ancient principle of fire.

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