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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energy efficiency, transformation from chemical to thermal energy, for district heating plants

If I have a system in which I introduce 100e.u.F (energy units) derived from chemical energy (i.e. fuel) and generate thermal energy to heat water what are e.u. absorbed by water? I.e. the efficiency ...
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26 views

What are physical effects that could be employed to emulate this system?

This is a simple system consisting of a tree of numbers such as ((1 2 (3 4)) (2 6) 1 6) and a rule of application, that states that a tree A applied to B is a copy ...
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50 views

What highest amount of energy can we get from a laser?

Can we get high energy from laser like fusion and fission reactions ? what is highest energy we can get from laser ?
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130 views

Collision of two deformable bodies - limitation of work-energy theorem

I am attempting to model the impact of a deformable body (clean, dry sand characterized as a continuous fluid) with flexible diaphragm (in this case a sheet of rubber). Assuming that this is a closed ...
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41 views

Welding physics (black body and heat conductance)?

If I have two pieces of steel that I would like to weld with a laser (say $d$ in diameter). If I wanted to melt the two pieces to a depth of $d$ along the edge and then combine them together, how much ...
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62 views

First-order pertubation theory

I'm having some trouble figuring this out, so I was hoping someone could help. I need to show that the first-order pertubation of the ground state energy is not changed by the pertubation $H'$, given ...
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0answers
56 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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364 views

How does the volume change affect an adiabatic process?

A gas consisting of rigid diatomic molecules was initially under standard conditions. Then the gas was compressed adiabatically, 5 times the original volume. Find the mean KE of rotating molecules ...
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1answer
85 views

Pendulum system: how is derived the output as Energy?

Good day to everyone, I want to understand in which way the "Energy equation" is been implemented to this pendulum system. $x_1(t)$: The angular position of the mass $x_2(t)$: The angular velocity ...
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58 views

Time reversed laser

Recently, I read an article on time reversed laser. I don't know why they call it a time reversed. I have a doubt that why they use two laser in the device. And what is an anti-laser? The device ...
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0answers
423 views

Nuclear reaction: creation of deuterium

A proton p collides with a neutron(at rest) n at relatively low-energies and creates a 'deuterium-core' d: $$p+n->d+\gamma$$ Find the wavelength for the photon as a function of the proton's ...
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1answer
2k views

Work being done without distance

I have this issue: If you push a 40.0 kg crate at a constant speed of 1.40 m/s across a horizontal floor (µk=0.25 ), at what rate (a) is work being done on the crate by you and (b) is the energy ...
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45 views

Elastic Collision Between Two Objects [duplicate]

Possible Duplicate: Elastic Collision And Momentum I've already asked this question, Elastic Collision And Momentum, but I didn't find the answer particularly helpful--sorry, I don't mean ...
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1answer
850 views

Momentum And Energy Problem

The information to the question is, "A $59.0~kg$ boy and his $38.0~kg$ sister, both wearing roller blades, face each other at rest. The girl pushes the boy hard, sending him backward with a velocity ...
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0answers
62 views

Energy can't be created or destoryed? [duplicate]

Possible Duplicate: Conservation law of energy and Big Bang? If energy can't be created or destroyed then how did the big bang create energy? and if energy can't be created then does that ...
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1answer
369 views

Faraday's law and superconductivity

According to Faraday's law of induction, volts = -Number of coils in a solenoid * change in strength of magnet / change in time. This doesn't take into account distance or speed, only time. If amps = ...
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682 views

Error Analysis, Change in momentum, Kinetic Energy

If momentum of an object is increased by 10%,then its kinetic energy will be increased by? Well, I don't need the solution logically by calculating the change in Kinetic Energy etc, but my question ...
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0answers
61 views

Taylor approximation of e(v) [closed]

Relativistic mass $\displaystyle m(v)=\frac{m_o}{\sqrt{(1-(v/c)^2}}$ $m_o$ = mass of object measured at rest $c$ = speed of light ($3\times 10^8\;m/s$) $v$ = speed If the total relativistic energy ...
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1answer
153 views

Proportion of energy compared to mass in universe

In Wikipedia (http://en.wikipedia.org/wiki/Dark_matter), there is a picture that shows us the proportion of matter and energy in the current universe - CMB. It seems to suggest there is nothing that ...
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162 views

2 streams going into an engine and 2 come out. Find the enthalpy?

Problem: Steam supply to an engine is made of two streams that mix before entering the engine. Stream 1 flows at a $.01\frac{kg}{s}$ with an enthalpy of $2952\frac{kJ}{kg}$ and a velocity of ...
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0answers
84 views

When will the moon fall down? [duplicate]

Possible Duplicate: Are tidal power plants slowing down Earth's rotation? I've heard that there are turbines converting energy from tidal waves. Tidal waves are created by the moon's ...
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2answers
3k views

How to calculate fuel consumption of car (mpg) from speed and accleration knowing mass, drag coeff and rolling resistance?

How can I calculate the current (instantaneous) mpg of my car if I know the speed and acceleration of the car? From reading various answers for the "car going level or up/down hill" question asked ...
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1answer
105 views

What happens to matter when in a thermodynamic equilibrium?

I am trying to gain a better understanding of thermodynamic equilibrium. Here's what (I think) I know: If a system is in Thermal, Radiative, Chemical, and Mechanical Equilibrium, then it is in ...
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2answers
182 views

What's the symbol behind Einstein's head? [closed]

What's the symbol called that's behind and to the right of Einstein's head in this picture? Bonus if you can tell me what the whole formula is!
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2answers
252 views

Do you need energy to exert a force?

Is force dependent or independent of energy?
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1answer
588 views

Power generator powered exclusively by gravity is possible? [closed]

According to this site, it seems so. Power generator powered exclusively by gravity:
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129 views

Stone vs. Atomic Bomb

What would do more damage, a B53, a 9 megaton uranium bomb, or a medium sized stone (2 kg) stone throw at 90% the speed of light. One thing that I know that will have to be considered is that fact ...
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3answers
149 views

Is the kinetic energy of an electron always $1.6 \cdot 10^{-19}~\text{J}$?

I was doing the following problem. For $d$. They bizarrely added an extra step. They calculated the momentum of the electron to find the De Broglie wavelength using the kinetic energy relationship. ...
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3answers
111 views

Is it possible to be changed Energy Unit in future or it is strict reality in nature?

Could you pease tell me why energy unit must be $Energy=Mass . \frac{Distance^2} {Time^2}$? (I tried to write general form of Energy unit) What is the strong proof of that unit? Does it just depend ...
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2answers
145 views

Energy required to reach 1 wavelength [closed]

I was curious if there was a forumla to find the energy required to reach 1 wavelength in a given substance. (or a vacumn if that's too hard). I am also wondering if this number can tell us anything ...
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3answers
2k views

Is kinetic energy a scalar? [closed]

Is it correct to say that kinetic energy is a scalar?
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2answers
664 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
208 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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1answer
52 views

how to use the energy work kinetic theorem [closed]

A single force acts on a $3.4~\text{kg}$ particle-like object in such a way that the position of the object as a function of time is given by $x = 4.2t - 2.1t^2 + 2.5t^3$, with $x$ in meters & $t$ ...
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1answer
88 views

Whether nuclear physics or nuclear engineering is suitable for doing research in nuclear fusion? [closed]

I want to do research in making nuclear fusion sustainable for electrical energy production , which field I should choose? and it is worth doing research in fusion now, since many of them are saying ...
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2answers
1k 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
90 views

Time difference in transmission of AC and DC

Is there any time difference while considering the transmission of AC and DC ? Is either one of them faster than the other one in terms of transmission of energy/power from one point to another? I ...
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1answer
154 views

The time is a type of energy ?

You know energy is necessary for the occurrence of an event . Time is also exactly neccessary for the occurrence of an event. If there is no time , there will be no event. I mean time is a type of ...
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1answer
257 views

Why are electrons in one atom attracted to negative electrons in another atom? [closed]

Why or for what purpose is this attraction purposeful or what is the reasoning behind why these energy particles are drawn to each other? Any proven results, or proposed theories of your own, or ...
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1answer
99 views

Determine KE of electron given momentum & mass [closed]

Some info: wavelength of electron: $2.78 \times 10^{-10}$ momentum of electron: $2.38 \times 10^{-24}$ Determine KE of electron. In a provided hint: $KE = \frac{p^2}{2m}$. So I have: $$KE = ...
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2answers
70 views

Changing Direction in a Vaccum [closed]

If a mass of one kilogram is traveling at one meter per second at 90 degrees, how much energy is required to get it to travel going 180 Degrees?
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2answers
359 views

Infinite Energy from Bobbing

Could this device theoretically continue in motion forever? If not, why not? (click below for images): Device description. Device process. The device is less dense than air, so it rises. The ...
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2answers
169 views

Why is the work positive here?

Problem http://apcentral.collegeboard.com/apc/public/repository/ap11_frq_physics_b_formb.pdf Please refer to question 1f Solutions ...
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1answer
71 views

4-momentum of massless photons

The time component of a particle's 4-momentum is $$ E'=\frac{E-up}{\sqrt{1-u^2/c^2}}\tag{1} $$ Now suppose it is photons that you are observing from a system moving at $u$ on a line towards ...
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1answer
85 views

To what does energy belong in an energy diagram?

I was reading this answer and I saw an energy diagram: Does the energy belong to the system or to the outside?
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1answer
94 views

How to heat water to 80°C? [closed]

I'm trying to figure out an easy water to get 80°c to consistently make the perfect cup of coffee. Let's assume room temperature water is 22°c. What is the ratio of boiling water to room temp water ...
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1answer
117 views

Quantum mechanics: Finite square well problem

What will happen if the potential is less than 0, for instance $V(x)=-10eV$. Is this means there will be no bound states? Since solution to the time independent Schrodinger equation (those discrete ...
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1answer
352 views

Spring launches a mass on an incline plane with friction, find the height [closed]

So I've calculated the answer to this problem, but my answer is different from my book's, so I'm trying to find the error. A spring with coefficient $k=600N/m$ launches a mass of $1.2kg$ from an ...
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1answer
30 views

Calculate amount of energy based on height of object

How can you calculate the amount of energy an object produces that falls from a particular height? Or water. In an eg i would like to know how can you calculate the amount of electricity water can ...
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1answer
29 views

Is watt unit depended on turbine speed

I'm new to electronics. I have a doubt. That is... Is watt unit depended on speed of turbine ? In my mind When turbine rotates fast the power in increase. Is it right ? Please help me. Thanks for ...