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

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What kind of research will go in nuclear fusion power once the commercial power plant is designed and implemented? [closed]

once the commercial nuclear power plant is built for electricity production , after this what kind of research does scientists do in nuclear fusion power. Why I am asking this question is ITER is ...
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231 views

Does time travel violate conservation of mass/energy? [closed]

Imagine I exist at time $t_1$ and my mass is $m$. At time $t_2$ I time travel back to $t_1$. At time $t_1$ there is now a net increase of mass/energy in the universe by $m$. At time $t_3 = t_2 - x$ ...
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111 views

Escape velocity problem

I was given a problem at school: How much Energy do we need to make a rocket of mass $m$ faster than the escape velocity so that it can travel in outer space? Here's how I worked: I know that ...
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75 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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61 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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110 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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94 views

Creating electricity from mains water pressure.

Could someone cleverer than me help me out? I had a crazy thought going through my head the other day and I can't lay my mind to rest until I get an answer. Q. How much energy could be produced by ...
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175 views

Different formulas for calculating power [duplicate]

$P=IV$, $P=I^2R$, $P=\frac{V^2}{R}$, what are the distinctions between these equations? How do you know which equation to use when?
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120 views

Is the potential energy of molecules related to its temperature? [duplicate]

Do ideal gases have a certain potential energy at a certain temperature?
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Classical disintegration of particles, Landau-Lifshitz series on Physics

i read Landau's book recently. In this book p.43 Landau says from (16.1) (16.2) can be write down $T_10$= $p_0^2$/2$m_1$=($M-m_1$)($E_i-E_1i-E_i'$)/$M$ For me, it is hard to understand the factor ...
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380 views

Energy transfer in elastic collision [duplicate]

In a given reference frame where object 1 (with known mass and velocity) collides elastically with object 2 (with known mass and velocity), can we identify which object loses kinetic energy? Is it ...
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124 views

Rigid body problem

I have some doubts about the next excercise: A bar of length $2a$ and mass $m$ moves freely with both of its extremes on a ring of radius $\sqrt2a$. The ring can rotate freely in a certain ...
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227 views

Is it true that a Space Shuttle launch is powerful like an “average” nuclear explosion?

Kind of an odd question here. First let's define what an "average" nuclear explosion is, because that's quite a controversial term - "average". Considering that the peak of nuclear tests was at the ...
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386 views

What is the maximum theoretical efficiency of heat to electricity conversion?

I know that heat engines (heat to kinetic) are limited by Carnot cycle and that kinetic energy to electric energy conversion via standard generator reaches over 90%. However I would like to know ...
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92 views

What does (simple) $j/cm^2$ represent AND how does this result $6.959j/cm^2$? [closed]

According to the image shown below, this specific Laser Hair Treatment device claims that it has a concentration of $6.959 j/cm^2$. So far by research I have found that it needs around $6\mbox{ to }7 ...
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62 views

Infinite mass in a coupled oscillator

Can someone help me with this? Imagine we have a system composed of three spheres 1, 2 and 3. 1 is connected to a wall on its left side with a spring and to sphere 2 with another spring, the sphere ...
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47 views

Transfered thermal energy to a gas with varying mass

In my physics book (and wikipedia) it states that the thermal energy transferred to an object is: $Q = c \ m \ dT$, where $Q$ is the transferred thermal energy, $c$ is the specific heat capcity of the ...
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56 views

Question about energy [closed]

Tom, weighted 60kg, set a world record of bunjee jumping, he jumped off at 223m height, and reached the lowest point when he's 50m above ground. If 30% of mechanical energy was lost when the cord was ...
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341 views

Pendulum water pump - apparent free energy

I've seen plans for a pendulum oscillator water pump that is claimed to pump a large volume of water (100 gallons) from a well of 100 feet deep. The pendulum consists of a 100 pound weight raised 6 ...
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326 views

Change in Wavelength of a Photon Relation to Energy (specifically Compton Effect)

Given a photon dropping from $\lambda_1$ to $\lambda_2$, its energy will drop from $\frac{hc}{(\lambda_1)}$ to $\frac{hc}{(\lambda_2)}$. However, I was wondering if there is any significance in the ...
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59 views

Yearly onshore wind turbine energy production [closed]

I am trying to work out the yearly energy production of an onshore Siemens SWT-3.0-101, hub height 94m, total height 144,5. Here is the power curve at each wind speed level worked out through a ...
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751 views

Internal kinetic energy and center of mass kinetic energy

For a given system, how can you tell which one is kinetic energy for center of mass and which one is internal kientic energy? K = Kcm + K int For example, "A 150 g trick baseball is thrown at 63 ...
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276 views

Hamiltonian operator apply to a wavefunction

When a Hamiltonian operator apply to a wavefunction, how could we write the hamiltonian as, $$H \psi = (E_n-\hbar \omega_0) \psi \ \ ? $$ Is this because $E_n= H+ \hbar \omega_0$? where ...
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288 views

Muon 3 Body Decay

I'm trying to calculate the maximum energy of the electron in the decay muon >electron + electronantineutrino +muonneutrino in the reference frame of the muon having no kinetic energy. $m_m$=mass of ...
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616 views

Solve a problem of work and energy

A man pulling sled of his daughter by a massless rope, climbing a snowy hill whose slope is equal to 15 °. Considering that the mass of the sled is $4Kg$, the girl's $26Kg$ and $\mu _c = 0,25$, ...
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825 views

Why does the amount of energy transferred depend on distance rather than time?

The change in energy of an object can be determined by the work equation, where work is the change in energy: $$ W = F \cdot d $$ I conceptualize the transfer of energy as simply a series of small ...
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392 views

Can we generate infinite energy by successive fission and fusion reactions?

Fission divides one Helium atom into two Hydrogen (Deuterium) atoms. And fusion, once again, puts together those two Hydrogen atoms into one Helium atom. In both reactions, overall output energy is ...
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163 views

Antimatter collision - Energy Released

I think it's about time for me to ask this question, as I've been contemplating this for a while. $$E = mc^2.$$ This is Einstein's most famous equation. But what does it mean? On my own, I had to ...
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884 views

Simple harmonic oscillator: zero point energy?

Today we had a lecture on the simple harmonic oscillator and its quantum mechanical treatment. My teacher derived the equation for it and finally concluded it has some zero point energy. My ...
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71 views

We create systems with different values of Energy? [closed]

I understand that Energy is a conserved quantity in a system. A number, that's always the same to the system. However, don't we determine such a number? I mean, we can create systems(Or study them ...
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120 views

what is “work”? (of a force)

I would like to know why two forces (of different magnitudes but same direction) that we'd use sequentially on an object to move it by the same amount twice, will produce two different values for the ...
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Work, Energy & Power - Body slides down a hemisphere

A small body of mass $m$ slides down from the top of a hemisphere of radius $r$. There is no friction between the surface of the block and the hemisphere. The height at which the body loses contact ...
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135 views

Question on communication between universes in a level 1 multiverse

Can matter, energy, or information travel from one universe to another in a Level I Multiverse? That is, is there any communication between Hubble volumes in an eternal inflation-induced multiverse?
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Electricity directly from heating a material [duplicate]

I am looking for some more information about how to obtain electricity from heat directly. This e.g. involves the Seebeck effect, as I have found it is called, where a material produces a voltage ...
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667 views

Minimization of energy and maximization of entropy

Are maximization of entropy and minimization of energy equivalent? Or are they contrary? Why should the thermodynamic potentials such as $G$, $A$, etc, be minimum at equilibrium? I am confused. ...
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Formulas for kinetic energy

I was reading ABC of relativity from Bertrand Russell and some formulas about kinetic energy caused me some problems. Here is the extract : The kinetic energy is, in the usual form ...
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290 views

A Calorimetry Problem

I have a question in calorimetry from an old competitive exam. The question is: The temperature of $100$ grams of water is to be raised from $24 ^\circ$C to $90 ^\circ$C by adding steam to it. ...
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571 views

Why doesn't a stationary electron lose energy by radiating electric field (as per coulomb's law)?

If an electron in a universe constantly generates an electric field why does it not get annihilated ? I am confused because I read that an accelerating charge radiates and loses energy. So, why won't ...
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Is it possible to “add cold” or to “add heat” to systems?

Amanda just poured herself a cup of hot coffee to get her day started. She took her first sip and nearly burned her tongue. Since she didn't have much time to sit and wait for it to cool down, ...
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250 views

Can there be energy with no force or energy with no power?

I think that both force (number of newtons) and power (p=ui(?)) implies that there is energy so we can't have force without energy and we can't have power without energy(?) But can there be energy ...
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350 views

Could arc reactors eventually be real?

Could arc reactors eventually be real? I have wondered about this, there is not much about it online. If they could how would they work?
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157 views

Potential energy and average force? [closed]

A body of mass $15\,kg$ originally at rest $5\,m$ above the ground falls and penetrates $15\,cm$ into soft earth. Determine the loss of potential energy Determine the average resistance of the ...
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174 views

Beta particle energy

what does it mean that a beta particle has a 1.6 MeV of energy , does it mean that it can ionize 120000 hydrogen particle with ionization energy of 13.6 MeV ?
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Not working brakes: just another energy conservation problem

A car is driving down a mountain ($v=90 km/h=25 m/s$, when the driver realizes that brakes aren't working. He try to lose velocity going up an inclined ($20°$) plane, with a friction coefficient of ...
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Energy problem: What's wrong here?

A car ($m=540\,\text{kg}$) engine, has a power of $60\,\text{kW}$. The static friction coefficient between wheels and road is $k=0.6$. How long does it take to reach the speed of ...
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124 views

What is the difference of work $W$ and thermal energy $Q$ in thermodynamic Stirling-process for ideal gas?

What is the difference of work $W$ and thermal energy $Q$ in thermodynamic Stirling-process (in simple form) for ideal gas? I think that you need work to preserve this process and you bring thermal ...
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130 views

How to get energy of collision if you know force of gravity of an object($m \rightarrow F=mg$)?

How to get energy of collision if you know force of gravity of an object($m \rightarrow F=mg$)? You get energy of collision by kinetic energy $E_k= \frac{1}{2}mv^2$, but if you use just force of ...
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Maximum Kinetic energy of a spring

The block in the figure below lies on a horizontal frictionless surface and is attached to the free end of the spring, with a spring constant of 35 N/m. Initially, the spring is at its relaxed ...
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284 views

How is there a connection between energy and information?

http://physicsworld.com/cws/article/news/2010/nov/19/information-converted-to-energy In the last part of the third paragraph of the above article it says: "In fact, Szilárd formulated an equivalence ...
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163 views

what to use for mass in a 2D FEM simulation

I am trying to find the energy of a wave travelling through a solid material in a 2D Finite Element Method (FEM) - Simulation. As a general approach I would try to use $E_{kin}=\frac{1}{2}mv^2$ at ...