Energy Definition and 999 Threads

The speed of star on the outer of are solar system is not according to the visible mass. Change the law of gravitation F = 1/r^2 to fix this. Galaxies far away are moving away with increasing speed. Change the law of gravitation F = 1/r^2 to fix this, include a repulsive force to fix. Would this...

From my understanding, quantum fluctuations create particle pairs that are usually annihilated. Is it possible to use some kind of force (eg: electromagnetism) to direct and separate antiparticles from normal particles? I believe experiments have proven that it is possible to store positrons...

I know that when it is ΔG>0 , it means there is no spontaneity, when ΔG=0 there is equilibrium, and when ΔG<0, there is spontaneity. But what happens when this is in the context of partial molar properties, when G is molar? I suppose molar ΔG is referred to a solution. Right? In that case, is...

Hello Forum, Energy, like space and time, is a common concept but little understood. I think Feynman himself stated energy is hard to describe... I have a few observations in regards to energy and I would like your feedback on them: While force, which represents an interaction between two...

Hi, I am calculating the binding energy of 11- Na- 18 Stats: Table of nuclides has BE/A = 6.202276 ± 0.006249 MeV m used = 18.026878252 amu E= mc^2 answer = 5.894327537620224 MeV Semi Empirical Answer = 5.919667778950925 MeV Including excess mass in E = mc^2 method 1 - Calculate...

First time posting in this part of the website, I apologize in advance if my formatting is off. This isn't quite a homework question so much as me trying to reason through the work in a way that quickly makes sense in my head. I am posting in hopes that someone can tell me if my reasoning is...

Hello! I need some help with this problem. I've solved most of it, but I need some help with the Hamiltonian. I will run through the problem as I've solved it, but it's the Hamiltonian at the end that gives me trouble. To find the Lagrangian, start by finding the x- and y-positions of the...

In the solid state physics by Ashcroft & Mermin, in chapter 9 there is a paragraph that I would be grateful if anyone could explain it more for me. The paragraph is: As it said in chapter 12 it will be seen. I read chapter 12 but unfortunately I can't understand what exactly it want to say...

If you search the net with the question: "Can clean energy replace fossil fuels?" then no clear answer is given. On the website https://blog.arcadia.com/top-7-questions-youve-asked-google-renewable-energy/ it is said: Yes! However, despite falling costs, wind and solar only produce a little...

A 2.2-kg measuring instrument is mounted on a balloon by your scientific team for atmospheric studies. At the top of its flight, the instrument is released from the balloon and falls most of the way back to Earth before a parachute opens. You are told that the magnitude of the acceleration at...

Please forward to appropriate subforums as I wasn't sure where to post it.In the standard model there are the composite particles and elementary particles, for the elementary particles there is said to be an associated field and the particle is the excitation of that field. Apart from asking how...

Suppose that we shined a source of light on a wall with infinitismal small opening. As the opening is infinitismly small, only one ray of light will pass through the opening ( suppose it has an intensity ##I_0##) and this ray of light will diffract into an infinite number of light rays with the...

Hello Can some one explain how you work out the combinations of quantum numbers for infinite wells in higher dimensions? For example if i have an energy level $$E_4$$ In a 2D well, then for quantum numbers does this mean the combinations allowed must be: $$4^2 + 1^2$$ $$1^2 + 4^2$$ So then...

Hello there :) if there were an energy converter for a motorway where 5000000 cars drive over it annually and that has an efficiency of 100 percent, how many kWh does the energy converter give me? The energy converter would generate 4000 joules / s per pass. (P = 1400 * 9.81 * 0.02 / 0.07)...

Welcome to PF! I'm an HVAC engineer and I actually gave a talk/round-table with the founder of your organization a few years ago: https://www.westchesterbiotechproject.org/innovation-in-research-2017 One factoid I give on labs that speaks to what people know is that a single 8' constant volume...

This is an example from my textbook that I am having trouble understanding. So the binding energy of Beryllium-8 is positive 56.6 MeV, so it means the nuclide is stable, right? My textbook seems to use the reference of positive binding energy as being stable. And so that means alpha decay for...

hi guys i saw this experiment in an old book that uses the gas vacuum tube "thyratron" for determining the hydrogen ionization energy , the idea i guess is straight forward : we set the filament current to a specific value then the electrons starts to emit from the cathode traveling its way to...

The answer is 1.1 J, but I don't know how to get there. The only equation I can think of that might be related to this is Intensity, which I've added above. I could find area, using .0004m as the diameter, and energy using 2.0 E 46 J, but I get stuck on energy.

Hello there.My question is:can Newtonian gravity be generalised to include not only bodies with mass but energy also?Thank you.Can my thread be moved to classical physics?

I found my energies for Potassium. I have 3.3 KeV for the k alpha nd 254.6 ev for L alpha, using z=19 and n=3. Are these values correct? Edit: I found the ratio to be .077

Hello, If I am trying to calculate the heat removed from a chiller system through this formula on engineering toolbox.com: Does COP or efficiency of the equipment come into play with this calculation? For example if a chiller is fully loaded isn't it running more efficient for a watt/ton...

I can solve the equation for a damped oscillator with a forcing function. I can then plot the Kinetic and Potential Energy. They will be out of phase, of course (KE peaking when PE is zero, and vice versa) And we know that when the input frequency is close to the natural frequency, the system...

Using the Newton's laws my result was h/hypotenuse and using the energy equations my result was h/D. My results are right ? And if so, how i justify the hypotenuse = D . Sorry for the bad english, the homework was poorly translated.

Given a particle in a 1D box with a finite number of states ##m##, is the probability a particle is in a certain state ##n## equal to the energy of that state divided by the sum of energies of all states? In other words, given $$ E_n = \dfrac{n^{2}h^{2}}{8mL^{2}}$$ is $$P_n=...

I know I just have to replace in the equation, I just want to know, is d=r=0.5 m or is d=2r, so r = 0.25 m ?

Hi, The enthalpy of crystallization of $KCl$ (Potassium Chloride) is + 715 kJ/mol. The enthalpies of hydration for Potassium and Chloride are -322 and -363 kJ/mol respectively. So, enthalpy of solution of $KCl \Delta H_{sol}=\Delta H_{lattice} - \Delta H_{hyd}$ $\Delta H_{sol}=715 kJ/mol -685...

I work in a Maldivian Utility Company. Our engineering team is pretty weak so I don't have anybody in the company to ask even though this is the state electric company. A supplier quoted us 2 CT meters . Rating for one is given as 1A(6A) and other as 5A(20A) which I believe is 1A basic current...

Following the method by Peskin and Shroesder 11.4 Trying to calculate the vacuum energy of a fermion. If my method is correct so far the next step is to find gamma function , the formula I have for gamma fuctions doesn't match this equation. Can anyone help with the next step? Starting with the...

I am looking for help on the following: a) Given the system shown in the figure below, derive the steady flow energy equation from first principle. b) Again using first principles, show how the energy equation would change for the case when the system is unsteady. I am trying to learn this...

Both alpha and beta radiations can only travel short distances through air as they're not as penetrating as gamma radiations. How long gamma radiations with 22 MeV energy can travel in air? Is it meters, kilometers, miles, etc. Is there a difference between a lower energy gamma ray and a higher...

Hello all, I have a community college student who is deciding on his major. He is really interested in Fusion energy and wants to pursue that path. He was in the Engineering Program and now, after doing some research, believes he should be in the physics program (A.S. degree in Physics). The...

Hello, When discussing alternative sources of energy, like solar, wind, etc., we often hear that if the energy produced by these sources which is not immediately used, can be "sent" to the power plant and used later... I don't think the idea that is energy being transferred "somewhere" and...

Electron can move from lower energy level to higher energy level when it absorbs energy equal to the difference between the energy levels based on equation: ##hf = \Delta E## If the incident photon has lower energy compared to ##\Delta E##, then electron won't move to higher energy level. But...

Draw graphs showing how interaction energy depends upon the relative orientation of two dipoles if (i) p1 is parallel to r, (ii) p1 is perpendicular to r. I've done the first part and found the interaction energy as UInt = 1/(4*pi*epsilon0*r^3)*[p1.p2-3(p1.r^)(p2.r^)] which I know is correct...

The hamiltonian ´for a free falling body is $$H = \dfrac{p^2}{2m} + mgy$$ and since we are using cartesian coordinates that do not depend on time and the potential only depends on the position, we know that ##H=E##. For this hamiltonian, using the Hamilton's equations and initial conditions...

Hello folks, a recent theoretical discussion with a materials engineer has left my head spinning, this sort of thing is beyond me but I am curious if any of the clever folks on here could solve my problem. I want to find the Force and Energy applied by my Indenter within the following...

"What is a tuned mass damper" by practical engineering From 6:36 to 7:07How does the energy of the pendulum tuned mass damper (PTMD) dissipate energy back into the building? Intuitively, it seems like it's momentum or resonance, where the PTMD is in phase with the motion of the building and thus...

I know that there is a boundary condition at ##x=0## where the wave function becomes zero however why are the allowed energy levels odd i.e. ##n=1, 3, 5 ..##

I am trying to relate these equations to get the energy with respect to momentum based on particle wavelengths. I did the following: $$\lambda = h/p$$ so $$p= h/ \lambda $$ Then $$p=mv$$ and $$E=1/2mv^2$$ So $$E = pv/2 $$ But the answer was: $$E = p^2/2m $$ I don't understand how they...

Hi PF! I don't understand the sentence: on one side says the energy is preserved, and, at the end, the total energy of the system will change if ##W## or ##Q## is added: ##\Delta{U}=Q+W##. Greetings!

Is the mechanism of greenhouse gases trapping energy emitted as Infra Red radiation by the cooling ground either reflecting back a 50% of the radiated IR energy back to Earth or/and the greenhouse gas molecule becoming excited with the extra energy and essentially becoming hotter? Is it just the...

Hi, Answer given is $E_n=29.4 Joules$ Here is the question. Answer provided by the Chemistry math expert/Professor is as follows but it is different from the answer given. How is that? Compressibility is the fractional change in volume per unit increase in pressure. For each atmosphere...

According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf the big pulsed power accelerator, HERMES III, generate electron beam with peak energy at 22 MeV and average electron energy at 16 MeV and the resulting photon energy which is bremsstrahlung radiation is approximately 2 MeV...

The question seems similar to the one asked here, https://www.physicsforums.com/threads/energy-in-everetts-many-worlds-interpretation.966266/ but since there didn't seem to be an answer I am asking it again in a slightly different form. I was watching a youtube video where Sean Carroll...

As summarized.

Hello there, I was trying to solve this problem. I have no problem with part A and C. But in part B, my guidebook arrived with different answer. Can anybody point out what my mistake is? I am using the same method as the elevator motor problem which states : "A 650-kg elevator starts from rest...

Hi, If we multiply $En=-\frac{2\pi^2me^4Z^2}{ n^2h^2} $by $\frac{1}{(4\pi\epsilon_0)^2},$ it is the formula of electron energy in nth Bohr’s orbit. Why we should multiply it by $\frac{1}{ (4\pi\epsilon_0)^2}$ a Coulomb's constant in electrostatic force? Where m=mass of electron, e= charge...

This confusion has lingered in the back of my mind for years now, would be good for me to finally get a grasp on this. Say I have an object currently at rest, and I use energy X to accelerate it to speed v. According to the standard formula, it now has a kinetic energy 1/2mv^2. Now I use the...

Hi, I have been reading a few literature regarding excess Helmholtz energy and I encountered this definition from the paper of Wong and Sandler (apparently, from the mixing rule used in a EOS): In particular, the ones in the red boxes. How did these equations come into being? I tried to look...

Here are the results from the python code: Odd results: Even results: I tried to solve for energy using the equation: I substituted the value for a as 4, as in the code the limit goes from -a to a, rather then 0 to a, and hence in the code a = 2, but for the equation it would equal to 4...