Energy Definition and 999 Threads

I don't really know how to proceed. Can someone help me out in this?

I want to know the difference between potential and potential energy. The potential is measured in volts and we provide potential ex 12V to a circuit. Some times we also say a potential energy to be applied to the electron ex. 1eV etc. I know eV is energy, but my question is do we need to...

m1v1+m2v2=m1vs'+m2v2' , if car hits small fluffy object m2, initially v2=0, and v1'=v2' ... so m1v1=[m1+m2](v2') but why not energy? Why is there a KElost? .5m1v1^2+.5m2v2^2=.5m1v1'^2+.5m2v'2^2 +KElost , and again v2=0, v1'=v2' .5m1v1^2=.5[m1+m2]v2'^2+KElost using consv of momentum...

I was just reading about the LIGO experiment wherein an interferometer was used to detect gravity waves. This interferometer uses opposed light waves, detecting if there is a shift in their wavelength due to stretching/squeezing of a gravity wave passing through the lasers. (I hope I'm saying...

Hello, Trivial question: a system is isolated and all its internal forces are conservative. Because of Newton's 3rd law, all internal forces are pairwise and the net internal force is always zero (regardless of the forces being conservative or not) hence the system's total momentum is conserved...

Hi!.. As known, a certain amount of energy is applied for compressing a mechanical spring. Thus mechanical spring is charged with energy and it stores it as elastic-potential energy. But whole energy, applied for compressing spring, can not be converted into potential energy. The reason is...

Hi Pf I read that in the light propagator there are loops of electrons. What would be the consequences if we could switch them off (or neglect them)? would it modify the speed of the photons?

Can you reverse entropy without using energy?

the answer in the solution book is 29K which only comes if I use mass for only one atom. ( They did not show any working ) My attempt: 1/2 x (1.67 x 10^(-27)) x (355)^(2) = 3/2 x 1.38 x 10^(-23) x T T = 29.48820652 K The confusion arises when I tried the following question: Q. Estimate the...

as I read here http://www.bbc.com/earth/story/20160429-the-real-reasons-nothing-can-ever-go-faster-than-light#:~:text=But%20light%20is%20made%20up,when%20particles%20like%20electrons%20cannot%3F&text=The%20natural%20energy%20they%20possess,are%20already%20at%20top%20speed. things with mass...

Summary:: Calculate the amount of energy in joules generated from 2 kg of uranium fuel if the uranium 235 represents 0.7% of the metal and every fission releases 200 MeV. Hi! I am stuck in this question from my exercise book : Q. Calculate the amount of energy in joules generated from 2 kg...

Hi, Planck's equation is written as E=hν where "E" is energy of a photon, "h" is Planck's constant having value 6.626 070 15 x 10-34 Js, and "ν", Greek letter nu, is frequency. Violet color has frequency range between 790–666 THz (Tera =10^12). If a violet photon of frequency 7.5 x 10^14 Hz...

I don't need the whole answer just a few tips to do it. I think it's something with the two different radiuses, but I'm really bad at this. We did a similar one in class, but there is a trick in this one that I can't figure out.

I am learning about capillary action of water. As water moves up paper. How is that not violating energy conservation as it is going against the force of gravity. This obviously can't be infinite energy.

So what I did first was calculate the initial and final potential energies with Epi=-9.433*10^11 m and Epf = -1.503*10^12 m. Then I found change in potential energy, -5.597*10^11 m. Using this I determined the change in kinetic energy, 5.597*10^11. I then added this change to the initial...

Hello, I would like to review and validate some concepts that I have been recently thinking about. Hope this is correct and useful to others that need to refresh these concepts. Forces can be classified as either conservative or nonconservative. Dissipative forces are always nonconservative...

I tried using U=3/2 NKbT, but i don't seem to get the correct answer..

Good day everyone, I've recently been researching direct energy conversion schemes for nuclear fission, and I have a question on the basic physics behind the device (specifically on how it converts kinetic energy to electricity). In essence, the "basic" scheme for fission DEC devices is that...

I know I'm probably overcomplicating this question, but I'm having a bit of difficulty coming up with a singular answer. I have a 4-foot diameter flywheel that I need to turn with an electric motor of an unknown horsepower. I say unknown because I I don't know what I need based upon the...

First, it is easy to see that n=4 after the collision because: E_1=-13.6\frac{1^2}{1^2}eV=-13.6eV E_4=-13.6\frac{1^2}{4^2}eV=-0.85eV E_5=-13.6\frac{z^2}{5^2}eV=-0.544eVBut, I never saw a definition for the width of an energy level. I tried to use something I saw online that said it was...

(a) Using COE, $$mgh = 0.5mv^2 + 0.5I\omega^2$$ I solved it, where $$\omega = 112 rad/s$$ (b) This is the part where I have question or problem. I saw my course mate working and he start of with finding centripetal acceleration. $$a_c = \frac{v^2}{r} = \frac{(r_0\omega)^2}{R_0}$$ Why isn't it...

$$R_{eff} = R_1 + \frac{1}{\frac{1}{R_2}+\frac{1}{R_3}} = 1.4 + 0.6 = 2$$ PD of R3 = 4 / 2 * 0.6 = 1.2 Net PD of the capacitor = 2- 1.2 = 0.8V $$ E = \frac {1}{2} CV^2$$ E = 0.8 ^2 * ( 3*10^-6) / 2 E = 9.6 * 10^-7 Correct answer is: 4.27 * 10^-7 was thinking if i should find the Effective...

1. If today vacuum and matter contribute 71 % and 29 % to the total energy density of the universe, at what redshift z were they contributing equally? 2. If today vacuum, matter, and radiation contribute 71 %, 29 %, and 0.01% to the total energy density of the universe, at what redshift z were...

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...