Energy Definition and 999 Threads

Hello everyone. I have a question that as simple as it looks it is making me doubt if I answered the correct solution. A room is illuminated by 12 double fitting 85W fluorescent lights and I got to calculate the energy consumption. I multiplied 12 x 2 because it says it is double fitting but I...

Hello. Be v grateful any assistance with this. Question is energy to haul 2000kg 4 metres up a 1 in 100 incline with 300 Newtons friction Answer is given as exactly 1.98 kJ. The only figures I can see that relate to anything here are 2000kg minus 10 = 1980, and 1:100 is 0.01 which times...

Assume that a contraption with loosely suspended internal weights is fixed to the body of a vehicle that is moving in free 3D space without gravitational sources nearby. Given the position and orientation of the vehicle as functions of time, how can one tell whether it is possible for the...

Summary:: Doubt in a spring exercise Text of the exercise "a mass of ##m = 0.4 \ \text{kg} ## is attached to a spring and it oscillates horizontally with period ##T = 1.57 \text{s}##; the amplitude of the oscillation is ##d = 0.4 \text{m}##. Determine the spring constant, the total energy of...

Hi there, I am doing a mechanical energy question. I think the solution is simple but I'm stuck on an algebra step. This is the solution but I am really not sure how they have simplified down to Va. For example I tried to factor out the m resulting in 1/2mv^2=m(1/2va^2+gh) Then I cancel...

Hello everyone. I need to calculate the annual energy consumption for a total of 6 electric devices. I got the following information: The A operation consumes 177 kWh 5 times a day for 6 devices for 250 days a year (9 operational hours daily) Each device consumes 113 kWh daily for 250 days a...

I am considering a system that includes a pn-region with N first then P, then a superconductor, but I am not interesting in the effect of the modes present due to the confinement of the p-region of the system on the conductance (from electrons to holes). How do negate these energy modes in the...

This is my understanding of the law of conservation of energy and the role non conservative forces factor into it. Could someone confirm if I have this right or explain where I am going wrong if I am? I would appreciate it. With the law of conservation of mechanical energy, ΔKE+ΔPE=0. This...

Hello. I have a question related to capacitance. here is another mechanical solution to harness wave energy. Can changing capacity of the capacitor be used to harness wave energy? Let's say we envelope conductive plates in plastic and submerge them in the ocean and the water in between them...

I started of by trying to find the work for I got stuck because I did not know how to solve for the Force. I solved for the distance by doing 3=d/5s which gave me 15m. but then I couldn't figure out where to go next in the problem because I don't know how to solve for (f) so an explanation would...

This is not my homework. I took it upon myself to answer a textbook question for mental stimulation. I wanted to know if someone can verify if these were the correct values that needed to be solved for, process, and final answer, and if not, what needed to be considered. For the initial...

I've come to a grinding halt with this and I can't see a way forward. Can someone please take a look at what I've done so far and let me know if what I have done is OK and then if it is, give me a hint on how to proceed. First up, Is ## u \cdot \nabla \cdot T = u_\alpha...

In Robert M. Wald's General Relativity he writes on page ##61##: The energy of a particle as measured by an observer - present at the site of the particle - whose 4-velocity is ##v^a## is defined by $$E=-p_a v^a$$ Thus, in special relativity, energy is recognized to be the "time component" of...

In this problem i don't find any way to obtain de kinetic energy in KJ/Kg because when i resolve the kinetic energy formula the result its: 1/2 (1300 kg/s) (9 m/s)^2 = 5850 kg * m/s (i don't obtain m^2/s^2, so KJ/Kg its not possible) In the potential energy (w) part i obtain this: m*g ( i don't...

This questions is hovering on my mind from a long time. Why would something which does not have life would want to be in such a beautiful neighborhood, while the world is so much disordered. What causes them to be in that regular array and how they choose which crystal structure is suitable for...

Hello, I was wondering if someone could help clarifying this question. The question asks to estimate the energy state difference between the vibrational ground state of S0,v=0 and the first excited vibrational ground state S0,v=1 of the spectra below. The given solution: S1,v=1 -> S0,v=1 at...

Let us attempt part C first, which is to find the total energy of the entire system. I can definitely find an expression for the force, as given by Coulomb's Law. However, why should I integrate this force from infinity to d, where d is the distance of the external charge to the centre of the...

I thought up of this problem myself, so I do not have solutions. I would appreciate if you could correct my approach to solving this problem. Firstly, the charge induced on the inner surface of shell B is -q, and so the charge on the outer surface of shell B is Q+q. The energy stored can be...

Here we are talking about non-relativistic quantum physics. So we all know kinetic energy T = E - V = \frac{1}{2}mv^2 in classical physics. Here V is the potential energy of the particle and E is the total energy. Now what I am seeing is that this exact same relation is being used in quantum...

I was looking into companies or startups that were doing things with motors to improve efficiency. I stumbled upon Turntide Technologies, which has a partnership with Amazon. Turntide is making a software-driven motor that "enables precise and reliable control to effectively use every watt of...

I get the first part of B, but why doesn't the transported direction not change as the electric field changes? Does it follow the right-hand rule?

I would like it very much if someone could give a hint on how to start this question. In particular, I tried to find the derivative of energy with respect to time, but that was not enough. Then I tried to apply the formula p * p = -m², but that also didn't get me anywhere. These were my two...

The conservation of energy equation is basically GPE is converted to KE of block and KE of cylinder. To get the correct answer, the KE of the cylinder is 1/2mv^2, where m is its mass and v is the velocity of its COM (which is the centre of cylinder). However, I viewed the cylinder as rotating...

Suppose a rocket is moving at radial velocity vr and tangential velocity vt in the Sun's gravitational field. At some time, the rocket enters the gravitational field of Mars (with the above mentioned velocities), and gravitation effects due to the Sun can be ignored. After more time, the rocket...

Wikipedia: "When a photon has about the right amount of energy to change the energy state of a system (usually an electron changing orbitals), the photon is absorbed." What happens if a somewhat higher energy photon arrives?

Hello! So here what I did is first calculated the potential energy; $$ E_p = \frac{1}{2} * k * x^2 $$ E_p should be = 0,125 J Now i tried calculating the kinetic energy, I used this formula $$ E_k = \frac{mv^2}{2} $$ to get v I used this formula $$v = x *\sqrt{\frac{k}{m}} $$ v should be =...

In Example 41.5, they are implying that, for a hydrogen atom, if the orbital quantum number ##l## goes down the electron will lose energy. However, they said nothing about the principal quantum number ##n## going down, so there should be no loss in energy. As far as this book has presented, the...

So I read that Bohr's atom has discrete energy levels that an Electron can orbit at and that each level has n amount of sublevels (if n = 2 then there are 2 sublevels). Does the sublevel that the Electron is in have to do with it's mass? Does an electron in energy level l and sublevel d have...

I'm trying to complete this past exam paper Q. Water volume = 200hl = 20000L 1L=10^-3 m^3 20000L = 200 m^3 Density of water at 15 deg C = 999 kg m^3 Density = Mass/Volume 999 kg m^3 = Mass/(200 m^3) Mass of water = (200)(999) = 199800 kg Heat required to to heat 199800 kg water: Q =m C dT =...

In most textbooks, the recoil energy of the nucleus is ignored as it absorbs so little energy, and since its main role in the reaction is to absorb some of the photon's momentum without absorbing much energy. I'm tempted to say that the nucleus gets the maximum energy when the kinetic energy of...

Suppose we have a molecule A-A and a molecule A-B . And we want to compare the differences in energy of the different molecular orbitals for example the 1s antibonding orbital with the 2s bonding orbital.How can we do that?

In using scintillator or germanium energy sensors, certain radionuclides representing some definite line energies are used to calibrate the sensors. What technique or method is used to measure or determine the energies of these standards.

How can we calculate the energy of a hole or an electron in p and n type semiconductors? Which are the contributions from different sources we must take into account? I know it is the dopant and base but if we change one of them how that changes it ? Maybe the interatomic distance has...

In ΛCDM, H(t0) = 70km/s/Mpc, Ωd(t0) = 0.3, Ωr(t0) = 0 and ΩΛ(t0) =0.7, so that Ω(t0) = Ωd(t0) + Ωr(t0) + ΩΛ(t0) = 1and the universe is spatially flat. I want to know the t and z when the matter density equal to the vacuum energy density. By total energy density equation, I think Ωd(t) +...

Thank you for reading :bow: Section 1 To find the energy states of the particle, we define the wave function over three discrete domains defined by the sets ##\left\{x<-L\right\}##, ##\left\{-L<x<L\right\}##, and ##\left\{L<x\right\}##. The time independent Schrodinder equation is...

The figure is as shown below a. From 0< t < t1 => 0 <t<4ms, the transistor is "ON" The circuit will become like this The current ##i_s = i_L##. To know the magnitude of the current ##i_L## do i need to know the impedance of the inductance or since it is DC voltage the impedance is not...

For one-dimensional binding potential, a unique energy corresponds to a unique quantum state of the bound particle. In contrast, a particle of unique energy bound in a three-dimensional potential may be in one of several different quantum states. For example, suppose that the three-dimensional...

I am currently studying Electrical Engineering and I have this question: An energy band is formed by the overlapping of atomic orbitals of atoms coming close to each other.I suspect that if the energy of the atomic orbital of the valence electrons of a chemical element is less than the energy of...

So force on a current carrying wire = ILxB. If I have a bunch of bar magnets making a uniform magnetic field of strength B, then a 1 meter long wire of 0 ohms carrying 1 Amp, the force on that wire is (1)(1)xB = 1B. If I let that force move the wire for a time T, let's assume the wire moved a...

Hi, In Problem 9.12 of Griffiths Introduction to Electrodynamics, 4th edition (Problem 9.11 3rd edition), in the problem, he says that one can calculate the average energy density and Poynting vector as using the formula I don't really understand how to do...

I try to use relativistic energy equation: $$E'=\gamma mc^2$$ But, I use $$\gamma=\frac{1}{\sqrt{(1-(\frac{v'}{c})^2}}$$ then I use Lorentz velocity transformation. $$v'=\frac{v-u}{1-\frac{uv}{c^2}}$$ At the end, I end up with messy equation for E' but still have light speed c in the terms. How...

The expectation value of the kinetic energy operator in the ground state ##\psi_0## is given by $$<\psi_0|\frac{\hat{p^2}}{2m}|\psi_0>$$ $$=<\psi_0|\frac{1}{2m}\Big(-i\sqrt{\frac{\hbar mw}{2}}(\hat{a}-\hat{a^{\dagger}})\Big)^2|\psi_0>$$ $$=\frac{-\hbar...

Summary:: Design compressed air energy storage for PV plant [Mentor Note -- Thread moved from a technical forum, so no Homework Template is shown] Hi All For a PV project of 5 kW, we will use a CAES. The preliminary design will consist of a compressor - 2 heat exchanger - Air receiver - air...

Hi, I understood that to calculate the available energy in these two reactions could be calculated from Ed = [Mn(X) – (Mn(Y) + m(e))] c^2, but when I have to change use the atoms' mass instead of the nucleons' mass, it gives out two different formulas : Ed = [M(X) – M (Y)] c2 for β- Ed = [M(X)...

A baseball is thrown and lands 120 m away. While the ball is in flight, assuming the effect of air friction is negligible, which of the following is true? a. At maximum height the ball has its greatest kinetic energy. b. The horizontal component of the baseball’s kinetic energy is constant. c...

Five electrons are in a two-dimensional square potential energy well with sides of length L. The potential energy is infinite at the sides and zero inside. The single-particle energies are given by (h^2/8mL^2) (nx^2+ ny^2) where nx and ny are integers. The energy of the first excited state of...

$$ \bra{ \vec{ p'}} T_{\mu,\nu} \ket{ \vec {p}}=\bra{\Omega}\hat{a}(\vec{p'})(\partial^{\mu}\Phi\partial^{\nu} \Phi-g^{\mu \nu}\mathcal{L})\hat{a}^{\dagger}(\vec{p})\ket{\Omega}=\bra{\Omega}(\hat{a}(\vec{p'})\partial^{\mu}\Phi\partial^{\nu} \Phi\hat{a}^{\dagger}(\vec{p})\\...

Now before i take a ton of beating I'm not a Physicist this thread was a google command away looking for a physicists. I am an entrepreneur from the Blockchain world and before that the IT world. Now with the Current World Economic Forum, green bonds and saving our planet conversations i would...

The textbook says that by squaring and subtracting the expressions you can eliminate u. E² - p² = y² (mc²)² - y²m²u²