Energy Definition and 999 Threads

A box of mass 25kg is pulled 5m across a smooth floor by rope with tension 22N. The rope is inclined at 40 degree to above the horizontal. There is a frictional force with average value 12N. The box starts from rest. Find the final speed. Iam getting the ans 1.97m/s. The textbook ans is 1.39 m/s...

Hello! If I have 2 energy levels split by something of the order of 10 Hz (they can be connected by an electric dipole moment i.e. ##\Delta J = 0## and they have different parities), what would be the best way to measure this difference (even 10% error would be good, but the lower the error the...

I've been noodling around with derivations of the relativistic energy and momentum, and I almost got it down to just a few lines. But not quite. I'm going to work in one spatial dimension, for simplicity (even though some derivations require a second spatial dimension) Let's assume that there...

Electrons rotate around a nucleus for long periods of time. Where does the energy for this motion come from? Ok, I realize that electrons don't actually rotate around the nucleus, like a tiny solar system. But if the electron is wave function, it's still constantly vibrating, constant...

Does "absorbing" negative energy from gravity cancel the upward momentum of the pendulum? Or what? Where can I see energy being negative? Does it repel stuff? It sounds impossible.

Hello, When you have a beta decay you get the typical continuos spectrum representing counts against the kinetic energy of the electron. But what's the shape and how I get the spectrum of the kinetic energy of the neutrinos? Thanks

A ramp rises 10cm for every 80cm along the sloping surface. A box of mass 50 kg slides down the ramp starting from rest at the top of the ramp. The coefficient of friction between the ramp and the box is 0.03 and no other resistance acts. The box is traveling at 2 m/s when it reaches the bottom...

A tile of mass 1.2 kg slides 3m down a roof that makes an angle of 35 degree to the horizontal. Find the decrease in potential energy. Iam getting the ans 24.8J PE = mgh= 1.2× 12 sin 35 ×3 The ans in the textbook is 20.6J

Ball A of mass 2kg, is moving in a straight line at 5 m/s. Ball B of mass 4kg is moving in the same straight line at 2 m/s. Ball B is traveling directly towards Ball A. The balls hit each other and after the impact each ball has reversed its direction of travel. The kinetic energy lost in the...

According to the wiki entry on Planck units, https://en.wikipedia.org/wiki/Planck_units, the energy density of the universe, 1.8 × 10−123, is 1/16th the cosmological constant, 2.9 × 10−122. Is there a theoretical reason for this precise relationship?

Energy of the One-dimensional box: ground state: En = (n^2*h^2) / (8mL^2), where n=1 twice the ground state: 2* En = 2 [(1^2*h^2) / (8mL^2)] Energy of the Three-dimensional box: En = (nx^2 + ny^2 + nz^2) *h^2 / (8mL^2) = 2 (1^2*h^2) / (8mL^2) As stated, twice the ground state energy of one...

Sean Carroll says that in SR the time component of the 4-momentum of a particle is its energy. It is of course also ##mc^2dt/d\tau##. He uses that to prove that ##E=mc^2##. Which begs the question why does ##E=p^0##? Misner, Thorne, Wheeler do roughly the same thing. I find these 'proofs'...

I have read that an electron requires certain minimum energy of threshold frequency to move an orbit However the energy needed decreases with increase in shell number The transition energy is reduced with each orbit For example The energy to shift an electron from 1st to 2nd orbit is much...

This question is for those familiar with the BCS theory of superconductivity or familiar with R.D. Mattuck's book “A Guide to Feynman Diagrams in the Many-Body Problem.” I am working my way through the book, and I am stumped by some of the problems at the end of chapter 15 (superconductivity)...

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In page 40 of Spacetime and geometry by Sean M. Carroll, when consider the classical mechanics of a single real scalar field, it reads that the field will have an energy density including various contributions: kinetic energy:##\frac 1 2 \dot \phi^2## gradient energy:##\frac 1 2 (\nabla...

But when I look at the definition of binding energy that doesn't make seem to make sense. It looks as though they had more energy when they were together and when they were separated that energy turned to mass (the mass defect)? Am I looking at this right? I also don't understand this...

Please help, I'm really struggling to understand how to work this... work = mass * gravity * change in height w = m*g*(h2 - h1) Total energy = Sum of potential energy + Kinetic Energy work = 1/2Kinetic Energy * Potential energy ^2 w = (1/2 * K) * U^2 m*g*(h2-h1)=(1/2*k)*U^2 rearanged =...

I am thinking about how an electric field has energy associated with it. If a single electron exists alone in a remote vaccuum, I believe it has it's own electric field surrounding it, and that this field has an energy content associated with it. My question is; does this electric field store...

Hello, I have 1 undergrad year left and was wondering what the most used programming languages in grad school are. I still don't know which grad school will accept me so I haven't bothered to ask them directly as my application will be in November when I get my GRE scores. I am Interested in...

ΔQ=mC(T3-T1) But, will this C be Cp or Cv. Both pressure and volume changes. So, neither of them can be. Feeling so confused

Hello! Assuming we can bring 2 energy levels very close to each other (e.g. by applying a magnetic field), what is the practical limit (in terms of lab equipment) on the smallest energy difference that we can measure? And what is the relative error on it, that can be obtained? For example if the...

It is claimed 2D Graphene sheets can be used to harvest thermal energy while being at the same temperature as the surroundings in seeming contradiction to Feynman's *argument (in the popular accounts). However, the academic papers referenced below make the claim everything is well within known...

It's been a few years since I failed my physics degree but I still really want to reach an understanding of QM, and I'm currently going through a QM textbook. One thing I cannot understand no matter how much I think about it, is momentum uncertainty. In classical mechanics a specific kinetic...

Let's say a mass is gently laid on top of a massless spring. The spring compresses. There is a change in the height of the mass. Therefore, there is a change in the gravitational potential energy: a decrease. The compressed spring now has potential energy (it has gained energy). The change...

If I hold a ball above the ground, it has potential energy. Once gravity pulls on it, it becomes kinetic. What is gravity and how does it convert one kind of energy to another?

Electrostatic energy involves a volume integral and a surface integral The question is how to apply this formula to a finite space in which case the 1st term (surface integral) won't vanish. Let's apply to a capacitor and enclose the capacitor by a closed surface. Calculate the energy integral...

Potential energy in a two-dimensional crystal Consider the potential energy of a given ion due to the full infinite plane. Call it##U_{0}##. If we sum over all ions (or a very large number##N##) to find the total##U##of these ions, we obtain##N U_{0}##. However, we have counted each pair twice...

Knowing that ##F(x)=-\mathrm{d}V(x)/\mathrm{d}x##, I found that ##F(x)=-2.4x^3+1.35x^2+8x-3##. But it was the only thing I could find. How can I analyze what will be the type of movement with the information presented by the question statement?

I don't have an idea of where to start. I tried to do Ein = 1/2 mv^2 ------ (1/2)(1)(10)^2 ----------- 50 but i don't know where to go from here

I have tried to apply the conservation methods, but I am not understanding what the statement is asking for.

The answer in the textbook says 0J but I am not sure what the concept behind it is. Does it have something to do with gravity?

Homework Statement:: Ionised atom, free electron, conduction band, donor energy level and acceptor energy level Relevant Equations:: None I have some confusion about the concept of some electronic bands and energy levels. Beyond valance band, in a solid crystal lattice, For an atom, can...

If I have a force that behaves according to the formula ##F(x)=\alpha x-\beta x^3##, how can I get the potential energy from it? I know that: $$-\frac{\mathrm{d}V(x)}{\mathrm{d}x}=F(x),$$ but what about the limits of the integration?

hi guys I am trying to derive the Gibbs free energy for a superconductor in the intermediate state , the book(Introduction to Superconductivity by A.C. Rose-Innes) just stated the equation as its : $$ G(Ha) = Vgs(0)+\frac{V\mu_{o}H_{c}}{2n}[H_{a}(2-\frac{H_{a}}{H_{c}})-H_{c}(1-n))] $$ I am not...

I want to do RF energy harvesting simulation for the measurement of Power Conversion Efficiency. So how can be simulation done on a single platform?. Kindly suggest

So, the Cp and Cv its very confusing for me. But, i understand what's its happening in this process, so, i use the logic and first i obtain a ecuation for obtain the final temperature ecuaticon: Q=m*C*△T Q=m*C*(T2-T1) T2=(Q+T1)/(m*C) If the process its in constant pressure, i use the Cp valor...

How to demonstrate that about 25% of the radiant energy in a cavity is concentrated between 0 and maximum energy wavelength?

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A few days ago a new dark energy map was published, which some claim "strays from Einstein's theory of relativity". To quote from the BBC News website: "Dr Niall Jeffrey, of École Normale Supérieure, in Paris, who pieced the map together, said that the result posed a "real problem" for...

I'm given an ultra-high energy cosmic ray with energy 10^20 eV. It is coming from a source 10 Mpc away with an extragalactic magnetic field with strength B = 10^-9 G. I am to determine the maximum angular deflection of this cosmic ray, so it hits Earth. I don't have an attempt of the solution...

The mass (rest mass) of an atom, for example, depends on the kinetic and potential energy of the particles and their individual masses. Kinetic and potential energy are relative. Why is the mass not relative, but the same for all reference frames?

If we look at system at constant temperature and volume which is galvanic cell, first law of thermodynamics states: $$ dU = dQ + dW' $$ Where W' is electrical work done by galvanic cell and Q is heat exchanged with surroundings. As far as I know electrical work is work done by electric field...

I almost always buy food from local market but recently I want to buy some rice (and probably other foods later) overseas which will be imported through our customs, so most likely the food will be scanned through x-ray or other high energy devices that I don't know, could rice grains or other...

Hi everyone, In my physics class, we are doing the Hollywood Physics Project. It's a project where you analyze the physics from a scene in a movie and talk about if it's accurate or not. I chose the scene from the Avengers where Thor strikes Captain America's shield with his hammer. The...

Why is the energy of a circuit placed in a magnetic field at infinity zero?

So far, I have found g of the foreign planet, Vf of the ball, and realize that GPEiA = KEfA (Am I right here?). Thus, since GPEiA = GPEiE, GPEiE also equals KEfE. I also understand that, since the same impulse is applied to catch the objects, both objects have the same momentum at the moment...

Answer: a) 7.35 m/s b) 216.09 m/s^2 *Is this correct?

Hi, I was reading the following article. Source: https://www.forbes.com/sites/startswithabang/2019/01/31/dark-energy-may-not-be-a-constant-which-would-lead-to-a-revolution-in-physics How come the density of dark energy remains constant? Yes, if it's intrinsic to the space itself and more...

Hi, If we are standing on the ground, the Earth applies a force equal to our weight to us, but why do we feel a greater force when we fall to the ground from a certain height? Our weight is the same along this small height because our mass and acceleration are the same and, even so, the normal...