Energy Definition and 999 Threads

E=hf-W where W is a work function. However we know that electrons in an atom will be excited only when radiated with photons of n*f0 discrete number of frequencies. where E=hf-W is a continuous function. Is this because energy level is continuous within a conductor? If we think of only...

I know the energy is ##\frac{q²}{ 8 \pi \epsilon_{0}}( \frac{1}{a} - \frac{1}{b})##, but I can't get this result using the second equation. What I did: ##W = \frac{1}{2} \int \rho V d \tau ## ##\rho = \frac{q}{ \frac{4}{3} \pi r³}, a < r < b ## ##V = \frac{q}{4 \pi \epsilon_{0} r}## ## W =...

Ve=0m/s Vp= 0m/s Qe/Qp= 1.60E-19 Me=9.11E-31 Mp-1.67E-27 Ive pretty much gathered all of the equations I think I need to solve the problem. I just am stuck. The last step I realize that the forces would be equal to each other so I have mp x ap = me x ae but then when I try to solve for the...

First, introduce the energy – momentum equation E² = p²c² + (m0c²)². Next, just think it in natural way. If the energy – momentum equation reflects the stationary situation, then, momentum p naturally equals to zero. Then, we got E² = 0 + (m0c²)², namely: E = m0c². It can be denoted exactly...

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1. The 4th line from the left, being the aqua blue line, corresponds to a wavelength of 486 nm, as blue light has a wavelength in the range 450-495 nm. 2. This is where I am having the most difficulty, I have tried to answer the question comprehensively but I am not satisfied with my answer. In...

If someone were to talk about "a non-physical energy source" would you consider that a contradiction in terms?

I learned that the energy operator is ##\hat{E} = i\hbar \frac{\partial}{\partial t} ## and the Hamiltonian is ##\hat{H} = \frac{-\hbar^2}{2m}\nabla^2+V(r,t)## If the Hamiltonian represents the total energy of the system. I expect the two should be the same. Did I misunderstand the concept of...

Hello, I am learning how to use calculus to derive the formula for kinetic energy now, I understandthe majority of the steps in how to do this, however, there is one step where I get totally lost, I will post a picture of the steps and I will circle the part where I get lost. If you see the...

I found the total work done is: ##\frac{q^2}{8\pi \varepsilon a} + \frac{q^2}{8\pi \varepsilon b} + \epsilon \int E_{1}.E_{2} dv## The third is a little troublesome i think, but i separated into threeregions, inside the "inside" shell, between both shell and outside both. Inside => ##E_{1}.E_{2}...

a. V=-GM/r V=-6.67*10^-11*6.0 x 10^24/6.4 x 10^6 V grav = -62531250 ~ -62.5M Jkg^-1 b. To find the gravitational potential 200 km above the surface of the Earth; r=6.4 x 10^6 +2*10^5 m=6.6*10^6 V grav=-6.67*10^-11*6.0 x 10^24/6.6*10^6 V grav= -60636363 ~ -60.6 M Jkg^-1 Can I check that it is...

Potential energy is generally a function of position vector ##\vec r## and it is defined as ##\int_i^f \vec F(\vec r)d\vec r=-U(\vec r) \bigg| _{i}^{f}=U(\vec r_i)-U(\vec r_f)##, where the force is conservative. Using the fact that the integral of force is also the definition of work, I obtain...

I got the right answers but have 2 questions. My first attempt was to use Equation 2 and solve for r then use Equation 3 and solve for n. My reasoning was that the photon needed to overcome the potential energy of the atom to release the electron. This gave me n =3.44. Why was I wrong? Then...

does an electron have kinetic energy when attached to a proton? if not, what is it transformed into?

m1 + m2 = 8 COE 0.5(m1)(u1)^2 + (m1)(g)(30) + 0.5(m2)(u2)^2 + (m2)(g)(30) = 0.5(m1)(v1)^2 + 0.5(m2)(v2)^2 + (m2)(g)(16) Can you check if my eqn is correct? And can you advise what to do after this? I wanted to do COLM but i don't know what is the initial part.

I often read of photons manifesting different levels of energy. I know that energy increases as wavelength decreases and frequency increases. Are there other ways particles gain or lose energy? As water boils heat energy is transferred to the water causing water molecules to move faster and to...

A recipient (cube) of 1m³ is filled of small spheres, there are for example 1000³ spheres inside the recipient. There are also 1000³ elastics that attract the spheres to the bottom. The elastic are always vertical. One elastic for each sphere. One end of the elastic is fixed on a sphere and the...

When A hits B, COLM mV = -mVa + 2mVb V = 2Vb - Va COKE 0.5mv^2 = 0.5mVa^2 + 0.5(2m)Vb^2 V^2 = Va^2 + 2Vb^2 When B hits C COLM 2mVb=4mVc Vc = 0.5Vb COE 0.5(2m)Vb^2 = 0.5kx^2 +0.5(4m)Vc^2 sub Vc = 0.5b mVb^2 = KX^2 After that I am stuck, cause i can't find V in terms of Vb only

Hello, The sigma $(\sigma)$ molecular orbitals are symmetrical around the bond-axis while pi $(\pi)$ molecular orbitals are not symmetrical. For example, the linear combination of 1s orbitals centered on two nuclei produces two molecular orbitals which are symmetrical around the bond-axis. Such...

There are two nonconservative forces in this situation, the work done by the person and the work done by friction - they are the only sources of work that change the total mechanical energy of the mass-Earth system. The initial energy (assuming gravitational potential energy is initially 0) is...

I always read that the weight of the protons and neutrons forming a nucleus is less than the weight of them if counted as standalone particles, the difference being the "mass defect" which goes into the binding energy to hold the nucleus together. So I have two questions. 1) The elementary...

To prove: total mechanical energy is constant with time where ##E(t)## is the total mechanical energy and ##V(x(t))## is the potential energy of the object-system. $$E(t) = 1/2 mv^2 + V(x(t))$$ taking the the derivative of ##E(t)## with respect time should give 0. in the third step in the...

I am not sure if i can explain my question properly. I am studying the Generators section in the magnetism chapter. As i mentioned the statement "The rate at which work is done is exactly equal to the rate at which energy is dissipated in the resistance". When the term dissipated is used does it...

I have a lot of questions about this single concept. You don't have to answer the questions in the order that I ask, if it is convenient to answer them in a different order. 1. When the dipole moment ##\vec{p}## is in the same direction as the electric field (uniform) it has the least potential...

I recall my memory when I was a high school student. I first learned about energy from Newton Mechanics. The only forms of energy involved are kinetic energy and potential energy. At that time, energy is more like a mathematical shortcut derived from F = ma rather than a concrete physical...

hello I would like some help with the first part of this homework. for the moment i have done this: E initial=m*g*h Efinal= 1/2 m*v ^ 2+1/2I*ω ^ 2 Ei=m*g*h+1/2I*ω ^ 2 Ef=1/2*m*v ^ 2 my doubt is with the potential energy since it confuses me when there is or not...

we know ##W_g = -\Delta U## but here to find ##\Delta U## we will need another equation won't it be wrong to write $$-\Delta U = -\int_1^{0.8}mgdy$$ as this equation is derived from ##W_g = -\Delta U## and as we have 2 unknowns we will need two equations. this is a rather easy problem but I am...

We know that Planck's constant is 6.626x10-34Js. Does the energy of the same numerical value 6.626x10-34J have any special meaning. Is it perhaps the lowest possible energy or are energies less than that energy theoretically possible.

I had a thought that I wanted to share in another thread, but it wandered way off track and quite properly was closed. But I thought the separate idea that I had spawned from the old thread was worthy of posting in a new thread. I do not want to re-open the old thread, though! In flat...

Constraint: ##I=I_{1}+I_{2}## ##P_{diss,R_{1}}=I_{1}^{2}R_{1}##;##P_{diss,R_{2}}=I_{2}^{2}R_{2}## We want to minimize ##P_{diss,TOT}=I_{1}^{2}R_{1}+I_{2}^{2}R_{2}## $$f(I_{1},I_{2})=I_{1}^{2}R_{1}+I_{2}^{2}R_{2};g(I_{1},I_{2})=I_{1}+I_{2}=I(constraint)$$ $$\nabla f= \left \langle \frac{\partial...

Hello everyone! I'm new to the forum, and I've been trying to solve a problem that seems farily but I can't still convince myself of having the right (or wrong) answer. Imagine you warm up one mol of for example potassium hydride from standard temperature 298.15K to 673.15K (400 deg C). It is...

I'm reading Schutz's A First Course In General Relativity and in chapter 5 he discusses an idealized experiment in which an object is dropped from a tower, then turned into a photon and sent back up to its original height. In classical mechanics we would say that as the object falls it loses...

I read this paper where if you take the alcubierre metric calaculations while including torsion in GR you get positive energy spin requirements instead of exotic matter. Here is the link: https://arxiv.org/abs/1807.09745 Could it be because a spinning quantum vacuum will be less stiff like a...

I know that by extremizing lagrangian we get equations of motions. But what if we extremize the energy? I am just little bit of confused, any help is appreciated.

https://www.asi.edu.au/wp-content/uploads/2016/10/ASOEsolns2012.pdf Q11 D) Markers comments: Few students reached part (d) and very few of those who did realized that the amplitude does affect the time taken for each of Mordred’s bounces. i.e. the energy losses results in shorter periods...

Hi, there. I am reading the article Relativistic quantum optics: The relativistic invariance of the light-matter interaction models by Eduardo Martin-Martinez el al (2018). Here he calculate the transition probability of a vacuum excitation for a detector. Suppose there is a lab where the...

$$\hat{T}_{\mu v}(x)=e^{i\hat{P}x}\hat{T}_{\mu v}(0)e^{-i\hat{P}x}$$, so $$\bra{\overrightarrow{P'}}\hat{T}_{\mu v}(x)\ket{\overrightarrow{P}}=e^{iP'x}\bra{\overrightarrow{P'}}\hat{T}_{\mu v}(0)\ket{\overrightarrow{P}}e^{-i\hat{P}x}$$ Now, $$\partial^{\mu}\Phi=\int\frac{d^3 k_1}{2\omega_{k_1}...

Hello I've written that homework statement as an example to illustrate my doubt: How can I tell if a force is conservative or not? I've read that, if the curl of the force is 0, it's conservative. But what about the friction force (##f=\mu N##)? Its curl is also zero, but it's not conservative...

Here is the figure: The answer is $$Q_A<Q_B$$ which I can show by calculation using the above equations. What's confusing to me is I thought that the change in internal energy was a state function. Which would mean since the initial and final points are the same, $$\Delta E_A=\Delta E_B$$ or by...

The question is simply why i can't use ∂U/∂V = -P? (

This question is an example in Durcell's Electricity and Magnetism. The solution goes as follows: [In this case] there are four different types of pairs. One type involves the center charge, while the other three involve the various edges and diagonals of the cube. Summing over all pairs yields...

In a parallel connection heat is produced. R1 = 5 Ohm R2 = 10 Ohm What is the relation of W1/W2? 1:4 1:2 2:1 1:8 3:1 I’d tend to say 1:2, but I am not really sure…

Because, ##F=ma=kv##, therefore, ##a=kv/m##. Clearly, the net acceleration ##A=-(g+a)##. Also, ##A=dv/dt=-(g+ \frac {kv} m )##, so cross multiplying and integrating LHS with respect to ##v## and RHS with respect to ##t## gives me: $$ v= e^{ \frac {-tk} m } * (u + \frac {gm} k) - \frac {gm} k $$...

I'm trying to understand if the amount of effort/energy required to get to absolute zero approaches infinity, or if its a linear thing... is there a point in which dropping near 0 kelvin changes from a 1:1 to an exponential curve? Is the whole thing a curve or is there a static point, like 1...

I thought I'd calculate how much heat was required to melt the Iron Throne, and then multiply that by the number of flame-gushes during the sack of Kings Landing, to get a total amount of energy expended. Then I'd convert that to calories and use the average number of calories per goat to...

I have a problem regarding Kinetic Energy which as we know is 1/2 m v squared. Say I have a 1kg mass moving at 10 meters/second. I have a 1 Newton rocket which I attach to the back and it burns for 1 second accelerating the mass by 1 m/sec/sec to 11 m/sec. The KE originally was 50 joules and it...

the gravitational potential energy of a body at any point is defined to be negative of the work done by the conservative force(gravity in this case) from bringing it to that point from a given reference point. if the reference point is taken to be at infinity and the potential energy at this...

Summary:: Would energy method give us a different answer from conservation of angular momentum? Hello, I do not know how to type equations here. So, I typed my question in Word and attached it here. Please see photos. Note: This question is not a homework. I did not find it in textbooks or...

In this system (consisting of just the gas) heat is transferred to the gas by means of a reservoir. So this means energy is added to the system. Does this necessarily mean that the work done on the lead shot due to an increased pressure will equal the heat that enters the gas? We are assuming...