Energy Definition and 999 Threads

I am given the answer is 2J and I know how to get there with U = q^2/2C. But what I don't understand is that why is the energy not conserved here? How can energy loses just because the capacitance is doubled?

I think I have a rough idea about it, but I am not sure whether it is correct. At least I feel that my understanding is a bit vague. Here it is: Globally (I mean across all worlds), the energy is conserved because the universal wavefunction evolves strictly according to Schrodinger equation...

So Ekf-Eki+Epf-Epi=0. I understand that the final potential energy is 0 (distance away approaches infinity), but don't get why the final kinetic energy becomes 0. If the final kinetic energy was 0, wouldn't that mean the object no longer has any velocity and would start being effected by the...

Hi, my question is that what is the main challenge of high energy physics? what is the best theory that maybe explain it and why it would not be accepted?

E= 3/2 (1.381x10^-23)(4x10^8)(2x10^19)50 E= 8.29 x 10^6 Wrong

Hello there, I have a question regarding this problem. I have no problem with part A. However, in part B, my solution manual states that the hollow cylinder will reach the bottom last. Why is it? I mean shouldn't the solid cylinder and the hollow one reach the bottom at the same time? you know...

I have used the heat equation and am not able to get the initial heat. This is what I have so far: 81060 = 7 * 140 * (change in temp) - (7 * 11300) + 7 * 140 ( change in temp) I found the change in temp to be 81.71K. But that does not help me with the initial temperature!

I have often read that dark matter and dark energy are now thought to comprise 94% of the total mass of the Universe. Just now I was reading an article which says that dark energy comprises 74% of the total. So, I'm confused about how energy can comprise mass. Dark matter, I can understand -...

I understand that the mass is being converted to energy but isn't it just an destructive interference of the properties of particles being present as waves of possibility , for example when electron is Interference with it self is it produce energy?, because the particle are weaves in quantum...

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...