Energy Definition and 999 Threads

  1. agnimusayoti

    Invariance of Energy Momentum Relativistic

    I try to use relativistic energy equation: $$E'=\gamma mc^2$$ But, I use $$\gamma=\frac{1}{\sqrt{(1-(\frac{v'}{c})^2}}$$ then I use Lorentz velocity transformation. $$v'=\frac{v-u}{1-\frac{uv}{c^2}}$$ At the end, I end up with messy equation for E' but still have light speed c in the terms. How...
  2. D

    Expectation value of kinetic energy operator

    The expectation value of the kinetic energy operator in the ground state ##\psi_0## is given by $$<\psi_0|\frac{\hat{p^2}}{2m}|\psi_0>$$ $$=<\psi_0|\frac{1}{2m}\Big(-i\sqrt{\frac{\hbar mw}{2}}(\hat{a}-\hat{a^{\dagger}})\Big)^2|\psi_0>$$ $$=\frac{-\hbar...
  3. Ameen1985

    Design a compressed air energy storage for a PV plant

    Summary:: Design compressed air energy storage for PV plant [Mentor Note -- Thread moved from a technical forum, so no Homework Template is shown] Hi All For a PV project of 5 kW, we will use a CAES. The preliminary design will consist of a compressor - 2 heat exchanger - Air receiver - air...
  4. duchuy

    Available energy in β+ and β- nuclear reaction

    Hi, I understood that to calculate the available energy in these two reactions could be calculated from Ed = [Mn(X) – (Mn(Y) + m(e))] c^2, but when I have to change use the atoms' mass instead of the nucleons' mass, it gives out two different formulas : Ed = [M(X) – M (Y)] c2 for β- Ed = [M(X)...
  5. H

    Question about the Kinetic Energy of a baseball in flight

    A baseball is thrown and lands 120 m away. While the ball is in flight, assuming the effect of air friction is negligible, which of the following is true? a. At maximum height the ball has its greatest kinetic energy. b. The horizontal component of the baseball’s kinetic energy is constant. c...
  6. H

    The energy of the first excited state of the system

    Five electrons are in a two-dimensional square potential energy well with sides of length L. The potential energy is infinite at the sides and zero inside. The single-particle energies are given by (h^2/8mL^2) (nx^2+ ny^2) where nx and ny are integers. The energy of the first excited state of...
  7. Diracobama2181

    Energy Momentum Tensor in Phi^3 Theory

    $$ \bra{ \vec{ p'}} T_{\mu,\nu} \ket{ \vec {p}}=\bra{\Omega}\hat{a}(\vec{p'})(\partial^{\mu}\Phi\partial^{\nu} \Phi-g^{\mu \nu}\mathcal{L})\hat{a}^{\dagger}(\vec{p})\ket{\Omega}=\bra{\Omega}(\hat{a}(\vec{p'})\partial^{\mu}\Phi\partial^{\nu} \Phi\hat{a}^{\dagger}(\vec{p})\\...
  8. E

    I Unleashing Solar Energy: The Potential of Mirrored Circles and Solar Panels

    Now before i take a ton of beating I'm not a Physicist this thread was a google command away looking for a physicists. I am an entrepreneur from the Blockchain world and before that the IT world. Now with the Current World Economic Forum, green bonds and saving our planet conversations i would...
  9. jjson775

    Energy - momentum relationship

    The textbook says that by squaring and subtracting the expressions you can eliminate u. E² - p² = y² (mc²)² - y²m²u²
  10. A

    Exploring the Possibility of Directed Energy for Hybrid Heating System

    Could directed energy fundamentals be used in active confinement by hybridizing the heating system with directed energy. I'm sure I'm wrong in this because I only have my high school diploma.
  11. Kaguro

    Fractional increase of energy vs momentum with relativity

    My attempt: ##E^2 = p^2c^2 + m_0^2c^4## ##2E dE = 2pc^2 dp ## ##\frac{dE}{E} = \frac{pc^2}{E^2}dp=\frac{p^2c^2}{E^2}## % (dp/p = 1%) ##=\frac{E^2-m_0^2c^4}{E^2}## % ##=1-\frac{m_0^2c^4}{E^2}## % ##=1-\frac{m_0^2c^4}{m^2c^4}## % ##=1-\frac{1}{\gamma ^2}## % ##=\frac{v^2}{c^2} ##% =0.81...
  12. B

    Energy within an electric field

    I am trying to calculate the energy within an electric field that is generated between two plates by a pulse but am unsure of what voltage value to use. The pulse is a sinc wave. I am assuming I can still use the equation ## E= \frac{1}{2}CV^2 ##. I know the ##V_{rms}## and ##V_{max}## which...
  13. naviakam

    High Energy Maxwell-Boltzmann distribution?

    If the high energy ion spectra is similar to that of Maxwell-Boltzmann distribution, possible to consider it as High Energy Maxwell-Boltzmann distribution? The ion spectrum is obtained due to the electric discharge in gas; and the peak energy is 30 keV and end point energy is 1.5 MeV and it is...
  14. B

    Formula for the energy of elastic deformation

    In every book I checked, the energy (per unit mass) of elastic deformation is derived as follows: ## \int \sigma_1 d \epsilon_1 = \frac{\sigma_1 \epsilon_1}{2} ## and then, authors (e.g. Timoshenko & Goodier) sum up such terms and substitute ##\epsilon ## from generalised Hooke's law i.e. ##...
  15. J

    I Quantum Tunneling in the Sun and Conservation of Energy

    Hi, In my textbook it says that if you consider the electrostatic repulsive barrier that protons in the Sun need to overcome in order to get into the range of the strong nuclear force to fuse together then it fails to fully account for the measured power output of the Sun. It says that the...
  16. T

    Energy transformed in a collision

    When reconstructing traffic accidents to obtain the collition velocities it is needed to obtain the "crush energy" which is the amount of kinetic energy transformed into permanent damage to the cars involved. From that kinetic energy we get the Energy Barrier Speed which is used with the...
  17. L

    How Does Potential Energy Dissipation Affect Temperature in a Metal Cube?

    Earlier today I've attended a physics exam and there is a query I'm not sure about. A metallic cube (specific heat capacity 30 cal/K*Kg ) falls from an height of 50 m on a non-conducting surface, and it stops. After the inelastic collision, what is the temperature of the cube? a_ The...
  18. jim mcnamara

    Energy Poverty in Australia: COVID Lockdowns Drove Costs Up 50%

    Article: https://phys.org/news/2021-01-covid-lockdowns-drove-older-australians.html -- Older Australians are having problems with energy poverty. Because COVID has forced them to stay at home and inside, heating and mostly cooling costs have increased by as much as 50%. Instead of going to...
  19. Leo Liu

    Conservation of energy in a CM system moving at constant velocity

    My book uses ##1/2m_1v_{1c}^2+1/2m_2v_{2c}^2=1/2m_1v_{1c}'^2+1/2m_2v_{2c}'^2## to show that the angles of deflection of the collision between two particles are the same in the centre of mass frame. However, I am doubtful that one can apply the conservation of energy to a "moving" system because...
  20. E

    Viscous work and dissipation of energy

    imagine two flat plates, the upper one moving with speed v in the +z direction, the lower one is stationary is the upper plate inserting work (per unit time) on the fluid system or the system exerting work on the plate? or both? why they don't cancel each other e.g if the fluid is receiving work...
  21. H

    B Apparent missing negative phase oscillation energy - where is it?

    When an oscillator produces waves - let's say they are highly focused - that are damped by a second negative phase oscillator, where is the wave energy? The energy in each set of waves must still exist. Has it become hidden?
  22. R

    I Some questions about the photoelectric experiment

    Background: self-studying. Very confused. Here are some initial questions I have about the photoelectric experiment. Some more may pop up later. 1. The book says we know photons exist due to energy considerations (such as emission or absorption). They also say that this photon energy is...
  23. F

    B Energy Conservation in Relativity: Perpetual Motion?

    This is very much, a ... what's wrong with this approach... Consider a large mass with no atmosphere, i.e. the moon. On it, construct a tower of arbitrary height. On the tower build an energy to mass machine, to convert energy to mass via E=mc^2. Once the mass is created, drop it from the...
  24. Firehanger

    I Is dark energy pushing or is it a mirror concept of gravity?

    Hey peeps, Ok, so I need some help here. I've just been watching some videos explaining the existence of dark energy and dark matter - something which has always fascinated me. These videos pose the theory that for the first 9 billion years of the universe dark matter ruled but, for the last...
  25. B

    Glass Thermal Energy: Solid Glass Beam w/ Spiral Column

    Could I put this on here for answers please ? If produced a solid glass beam with a spiral column thorough the middle of it would the core be hotter or cooler than the surrounding air? If colder could it be use in conjunction with ground source technology to produce hot water? I not sure how to...
  26. zonde

    I Interpretation of Potential Energy as Field Property

    I will quote this statement from another thread: In that thread number of other posters seemed to agree with this statement. So I tried to analyze it a bit. For the sake of my questions let's say we limit GR to Schwarzschild spacetime and if there are problems with gravitational potential...
  27. M

    Energy landscape in the two state model (Boltzmann distribution)

    From an excel file I can get the probability of each energy state Εi and I saw at Wikipedia that the probability of each energy is proportional with e^−Εi/KT, from this I find the energy of every micro state. Also from the formula which I found on a paper I can get a curve like the curve...
  28. J

    Energy paradox in classical electrodynamics?

    Consider two massive charged objects at rest with a large horizontal distance ##d## between them (object ##1##: mass ##m_1##, charge ##q_1## and object ##2##: mass ##m_2##, charge ##q_2##). I apply a constant vertical force ##\vec{f_1}## upwards to object ##1## so that it gains an acceleration...
  29. A

    Confusion about tidal locking and rotational kinetic energy

    Hello! I was reading two things: 1) tidal locking (as explained in the Wikipedia article:https://en.wikipedia.org/wiki/Tidal_locking where it is stated that, because of internal friction caused by the body of water being attracted to the moon and deforming, the kinetic energy of the system...
  30. G

    Change in Internal Energy in Accelerated Gas Chambers

    Summary:: How internal energy changes in a acclerated cabin. There are two tourus shaped insulated closed pipes containing equal amounts of ideal gas under same conditions. B has a adiabatic partion wall. If both are to change angular velocity by w radians per second. How internal energies...
  31. O

    Law of Conservation of Energy Problem: Trampoline

    For a) I did Eg = Ee + Eg and tried to solve for x. I got 5.4 m but I think this is wrong. I have no idea how to do the rest, please help :')
  32. F

    Minimum energy of a photon to produce ##\pi^+##

    I have a doubt about the first request: I suppose to find the minimum energy of ##\gamma## in the situation where ##p## is stationary, there is no reason to say that the proton is stationary if I were to calculate it in the CM, right?. So I have to consider che LAB-frame to find ##E_\gamma##...
  33. F

    Interpreting Energy diagrams for polyatomic molecules

    Hello, I am trying to correctly interpret the energy diagram below. For example, a diatomic molecule can translate (kinetic energy), rotate (rotational energy), vibrate (vibrational energy). Each different type of energy is quantized and has associated modes (also called states). The...
  34. M

    A Why Do We Need Alchemical Methods to Compute Gibbs Energy Changes?

    Hi, To compute, for example, the Gibbs energy change for a ligand binding to a protein, various so called alchemical methods are used in molecular dynamics simulations. My question is why can't we just obtain averaged Gibbs energies for 1) the free ligand and protein in the same water box, and...
  35. mattlfang

    A ball hitting a two-ball system (with a spring between them)

    I honeslty don't quite know how to start. It seems like the Hooke's coefficent k is independent of the answer to this problem. I would also appreciate any clue of expressing the condition when "balls will collide again". The fact that all balls can keep moving make this rather difficult. It...
  36. F

    What is the difference between internal energy and enthalpy?

    Hello, In thermodynamics, with systems being represented by gases (can liquids be also included?), the internal energy ##E_{int}## of a system represents the total kinetic energy + the total potential energy of the system: $$E_{int} = KE_{tot}+ PE_{tot}$$ The term ##KE_{tot}=Q## is also called...
  37. A

    Can Mechanical Energy Be Conserved in an Accelerated Frame?

    In the frame of the accelerated block, I applied the non-inertial force F'. My doubt is if I can conserve the mechanical energy in the accelerated frame and find the speed at the top. Otherwise, how could you proceed.
  38. B

    I "Packing of energy" question related to the ultraviolet catastrophe

    Hi, I'm curious about the ultraviolet catastrophe, and how Planck decided to hypothesize the quantization of energy integrally proportional to frequency to explain the drop off of energy in the higher frequencies. So what I don't understand is, when the energy is transmitted as a photon, does...
  39. sahilmm15

    Other Maintaining psychological energy levels

    Many of you would have heard about physical energy levels. Like maintaining the physical energy throughout the day so that you do not get tired. People recommend exercising, meditating etc etc. But I found out that my mental energy drains at a very rapid rate. I wake up with full energy but...
  40. E

    I Recovering Newton's energy conservation law for an Earth's lab

    I'm looking at Schutz 7.4 where first he obtains the following expression for a geodesic: $$ m \frac {dp_\beta} {d\tau} = \frac 1 2 g_{\nu\alpha,\beta } p^\nu p^\alpha $$ This means that if all the components of ##g_{\nu\alpha }## are constant for a given ##\beta##, then ##p_\beta## is also...
  41. O

    Law of Conservation of Energy Problem (kicking a soccer ball)

    a) So far, I have equated Ek to Eg to solve for h. 1/2(m)(27)^2 = m(9.8)h. I haven't taken the angle into consideration. I'm not sure if I have to use the x or y component. I got my answer to be 37m but again I don't believe this is correct. b) I did Ek = Eg + Ek. 1/2(m)(27)^2 = m(9.8)(3.5) +...
  42. Qwet

    I Conservation of energy in general relativity

    Hello. I have a question about the law of energy conservation in GR. As time is inhmogeneous, we don't have energy-momentum 4-vector which would be preserved during system's dynamical change. It is only possible to define 4-vector locally. And next, the problem regarding how to sum this vectors...
  43. T

    Gravitational Potential Energy on an Incline

    Hi, When regarding Gravitational Potential Energy, I know the formula is U=mgh. However, when the object is on an incline (say at an angle of 52 degrees) would it still be mgh or something else? (This isn't homework I simply was just curious).
  44. Incnis Mrsi

    I Infrared energy flux from the Moon

    I am interested in energy flux density from the Moon at Earth’s surface, specifically in infrared (albeit most of it comes in infrared anyway). Physics.SX (boyfarrell) gives an estimate 89 mW/m². I doubt it for several reasons. 400 K (as effective mean) on Moon seems to be unrealistically hot...
  45. J

    B Are energy bands in solid state timeless?

    The wave function or Schroedinger equation is timeless, correct? You can reverse the equations and forward it. Our arrow of time comes due to decoherence in macroscopic object. How about energy bands in solid state. Do you consider it as timeless wave function, or is it decohered?
  46. Adams2020

    What is the recoil energy of a nucleus produced in its first energy level?

    Table: To solve, using the conservation of energy: E0=(m(deutron)+m(16O)-m(17O)-m(p))c^2 so: E0=(2.014+15.994-16.999-1.008)931.5=0.93 MeV. so using the conservation of energy: 14.95+0.93=16.62+0+E' E'=- 0.74 MeV But the energy sign has become negative. I also calculated for the first excited...
  47. E

    Energy current for field satisfying KG equation

    First to compute the time derivative of ##\mathcal{E}##,$$\mathcal{E}_t= \phi_t \phi_{tt} + c^2 (\nabla \phi_t) \cdot (\nabla \phi) + m^2 c^4 \phi \phi_t = \phi_t \left[ \phi_{tt} m^2 c^4 + \phi \right] + c^2 (\nabla \phi_t) \cdot (\nabla \phi)$$Then we switch out ##\phi_{tt} + m^2 c^4 \phi##...
  48. E

    I Solving Relativistic Inelastic Collisions: 150 GeV Energy

    Hi! Hope I'm posting this in the right place! I'm practicing for exams and came over this question: A proton with mass ##m_p## is accelerated to a relativistic velocity, with kinetic energy ##K##. It collides completely inelastic with another proton, which has the same kinetic energy, ##K##...
  49. J

    What effects does an electric field have on potential energy?

    Like an electric field is applying a sort of force on a particle. I was wondering if this at all impacts the potential energy of a particle. For instance, when the force of gravity does work on an object, its potential energy changes as a consequence. Would it be the same thing here?
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