1. S

    Energy Definition

    Let's say one gallon of fuel can make a spaceship rocket engine with a mass M to run for 1 hour and to create a constant acceleration A. If we will use the full gallon starting from zero velocity, we will reach a velocity of A*1=V, the kinetic energy of the spaceship then will be Ek=0.5MV^2 . We...
  2. H

    Use Conservation of energy to solve projectile motion

    Hello, I’m working on this homework problem and am having trouble finding a way to explicitly solve for initial velocity. I got a hint from my professor that the final point should be at the top of the parabola, but I may have misunderstood him. We solved this using kinematics when we were on...
  3. T

    understanding energy loss in compressed air system

    When measuring pressure drop across a compressed air system shown in the included figure, I get different results depending on the system downstream of the actual component I am measuring pressure drop across. Btw this is a real experiment that has been ran. The numbers below are different but a...
  4. C

    Quantum entanglement energy

    Hi all I’m an average guy with a question. If you can split a particle separate them by any distance, apply a force to one and the other will behave in the same manner, why aren’t we sending one half into space exploding it in a nuclear blasts and have clean energy from the remaining half on...
  5. I

    zero point energy ?

    Hi I am new to this forum. I do not know if anyone on this forum can answer this question. But here goes:- I have an interest in QED, and was mildly interested in Bohemian mechanics. Recently I read a link on Stochaistic Electro Dynamics and zero point energy, here is the link Calphysics...
  6. G

    Electron-Positron Annihilation, low energy vs high energy mode- do both end in 511 ke

    Electron-Positron Annihilation, low energy vs high energy mode- do both end in 511 keV Annihilation? Normal room temperature electron-positron annihilation is a well documented process, used in industrial, medical and metroloogy fields, among others. There are two modes of e-p...
  7. B

    Definition of Gravitational Potential Energy

    Can anyone explain to me the definition of gravitational potential energy? I mean, i understand that it is 'the total work done in bringing a mass from infinity to the point' for any mass at a point, but it just seems too vague. For instance, why is it zero at infinity and negative nearer to the...
  8. P

    Energy conservation in mixing streams

    Is it correct to apply two separate Bernoullis equation - for sections 1-3 and for 2-3? Why/why not? I ve seen such solution to this problem on the internet but I have some doubts. I think that energy between sections 1 and 3 is not conserved because of energy exchange with the other stream...
  9. C

    Energy leakage from a waveguide

    Are the electric and magnetic fields within a waveguide operating at microwave frequencies visible outside of the waveguide? If I connect a probe across different points along the exterior of a waveguide, will I see a signal? If I loop an insulated wire around the outside of a waveguide, will...
  10. J

    Energy of band of d-dimensional semiconductor when voltage V is applied across

    Let's say we have a one-dimensional semiconductor and I apply voltage V across it, I want to calculate the energy of a parabolic band, when a source and drain voltage is applied across it. I expect it to be $U = \Sigma_k \frac{\hbar^2 k^2}{2 m^*}f(k)$ where f(k) is the fermi function. When no...
  11. T

    Origin of Gibb's free energy

    Gibb's free energy gives the energy which is easily available in the system, it can be used to do work. But I wonder what is the origin of the Gibb's free energy? Can anyone explain at the molecular point of view? As in, say the electrons are in a random state of motion, so the collective energy...
  12. Cervesa

    More on work and energy

    Why are you seeking affirmation on an academic help forum? Why not submit your findings to a physics journal for peer review?
  13. L

    Internal Energy in isolated system

    Hello, I have an isolated system (no Heat, Work exchange with environment). The 1. Law of Thermodyn says deltaU = 0 for such a system. Then I consider NaOH (solid) and water in this isolated system. The solving process creates entropy (entropy production=irreversible). Temperature...
  14. P

    Calculating Mechanical Energy

    Hi Everyone, I can't seem to figure this problem out. Please help! 1. The problem statement, all variables and given/known data A ball was launched upwards and vertically at a speed 3 m/second up to a height 4m. Calculate the mechanical energy of the ball if its weight is 5 Newtons...
  15. J

    Water Heater - useful energy content

    Hi, i´m developing a project and have some questions about thermodynamics I have this table with data. And this is what variables are: -useful water flow rate (f) means the minimum flow rate, expressed in litres per minute, -useful water temperature (Tm), means the water temperature...
  16. O

    Work and Energy

    Energy and Work Hello! I have made big discoveries about Energy. These discoveries completely change our understanding of the universe and give us access to new clean Energy. The Revolution in Science. The Biggest Ever Discoveries in Physics. The New Inexhaustible Energy...
  17. B

    Ionization Energy Help

    Hello everyone, this is my first time posting here so apologies if this is not the appropriate place to put this. I was going through exam review and found a question that is tripping me up. It is probably a pretty simple solution and I just can't see it because I've been looking at it too long...
  18. S

    Internal energy level configuration of cerium ion doped into a lanthanum fluoride

    Internal energy level configuration of cerium hi, I am a graduate student in my third (research) semester. I am reading an article for four days but not getting this diagram. Can anyone explain this diagram for me?
  19. Z

    Energy and Work (pV diagram problem)

    Hi there! So I've never taken physics until now (first year in uni) so I'm struggling to say the least. I'm trying to do this problem of a pV diagram and I'm stuck on b). I've done a) and c). I'm just confused how to find Vc in an isothermal process because if it was adiabatic then I could use...
  20. B

    Stress energy tensor transformation

    Show that if you add a total derivative to the Lagrangian density L \to L + \partial_\mu X^\mu, the energy momentum tensor changes as T^{\mu\nu} \to T^{\mu\nu}+\partial_\alpha B^{\alpha\mu\nu} with B^{\alpha\mu\nu}=-B^{\mu\alpha\nu}. (Note: the Lagrangian can depend on higher order derivatives...