Energy Definition and 999 Threads

The answer says it decreases but shouldn't it increase? according to the kinetic model, KE accounts for particle vibrations. PE accounts for the attractive forces between particles. Since condensation means gas -> liquid, it means the particles become closer and hence the attractive forces...

Hi all, I hope someone can help me with this: I am working with wien2wannier to obtain Wannier functions from wien2k calculations, but I am struggling to define the energy window needed for the init_w2w. The outputfind file shows emin = -999.00 eV, emax = 999.00 eV, and efermi = 0.6124 Ry...

Hi For a personal project, I am seeking papers or information on the energy level diagrams (where the y-axis is energy (eV)) for Lithium Nitrite (LiNO2) and di-oxygen (O2). I tried the internet and science direct (www.sciencedirect.com) but to no avail. Any help in this matter would be...

[Mentors’ note: No template because this post was moved from the technical forums. Everything that the template asks for seems to be present in the body of the post] Suppose there is a spring-mass system arranged as shown in my crude drawing. This occurs on a frictionless surface. The spring...

My approach to the problem was to try using Q = cmΔt by rearranging it to solve for Δt=Q/cm. Since the power per person is 70 W, there are 1800 people in the concert hall, and the problem asks for the temperature rise over two hours, I multiplied 70 W×1800 people × (3600 sec × 2) which gave me...

I'm 64. My background prior to 2001 - Aviation, experimental aircraft and aerodynamics, robotics, mechanical and software engineering, disaster recovery. Since 2001 - Human sustainability and global recovery, researching every related sector in depth in order to understand what can now be proven...

no clues

In nature how and where is energy converted to matter, where do the necessary conditions exist, is the process well understood, pure theory, or not understood at all?

For the right hand side I expressed each of the quantities in SI units, $$C \cdot \frac{kg}{A \cdot s^{2}} \cdot m$$ Then substitute newtons in as ##N = kg \cdot ms^{-2}## and we get, $$C \cdot \frac{N}{A \cdot m} \cdot m$$ Using the definition of work as ##J = N \cdot m## and Amperes as...

I am not sure what the context of the question is. I am thinking this question is about light bulb emitting different colour at different temperature. The higher the temperature, the lower the wavelength hence the higher the energy emitted by the bulb so the energy consumption will also be...

Imagine an electric field between two charged plates that is so intense that its energy density is enough to produce real electron-positron pairs. These electron-positron pairs annihilate to produce photons that radiate away. Does the electric field between the charged plates regenerate so...

Hello All, I'm trying to simulate in MCNP the energy response of a PIN diode. To do this, I have modelled a "slab" of silicon in an epoxy case at 2cm away from the source and with the F8 tally set to 25keV bin increments to 1MeV, I do as follows: Set the source energy to 33keV Run the...

When there is a probability involved with an energy state, e.g. with partition function, why is total energy the same as average energy (if it is). Just want to make sure - is this just a definition? Thanks

Energy required to evaporate water. Given 3 evaporating scenarios: 1. Glass filled with 50cc of water at 20C; the water is heated to 60C 2. Glass filled with 50cc of water at 20C; the water is heated to 100C 3. 50cc of water at 20C wiped over a large plate to create 50micron thickness layer...

I've mentioned the problem that i'm facing in the question that I've posted. Kindly go through it.

The following is what is written in the book I am reading. The energy required to "push" the mass into the system is $$F\delta z=PA\delta z=PV\tag{1}$$ in which ##V## is the molar volume of the closed system, ##F## is the acting force, ##A## is the cross-sectional area, and ##\delta z## is...

Imagine a projectile with density p, initial velocity v0 and initial stagnation pressure = 0.5p{v0}^2 being fired into the gas chamber with a final gas pressure given by Pg = nkT, for n being the final number density before (at max pressure of gas) and T the corresponding temperature of the gas...

I have a thought experiment in mind. Crudely speaking, the second law of thermodynamics implies that there is only a finite amount of change possible in the universe. Once this limit is reached, no more change can occur. The key thing here though is reversibility. If changes were reversible...

Let me start by saying the idea isn't mine at all. It's actually somewhat usual within Science Fiction works. Maybe one of the most popular appearances of the concept is the videogame Stellaris where there is commerce with aliens so a universal currency is very convenient. In economics, money...

The answer from the textbook is: Use energy conservation ## \frac{1}{2}mv^2 + \frac{1}{2}I_{cyl}w^2 = mgh_{cyl} ## ## \frac{1}{2}mv^2 + \frac{1}{2}I_{sph}w^2 = mgh_{sph} ## Subtracting the two equations, eliminating the initial translational energy, we have: ## h_{cyl} = \frac{v^2}{g}...

Is it possible to solve this without knowing the radius of the cylinder? My initial thoughts were that the energy required to stop it would be the sum of its rotational and translation kinetic energy, but I'm not sure it can be calculated without knowing the radius.

Hi, I love the lectures by David Tong. Usually I can follow his calculations (but I am not yet so far into the lectures...). But one that I just cannot do is the derivation of the energy in (4.16), the expression being ##E = \frac {mk^2} {2 l^2} (e^2 - 1)##, where l is the constant angular...

I'm not quite sure how to apply conservation of string to this problem, so guidance would be appreciated. Normally as long as there isn't a "sub-pulley" I can do the problem fairly easily but this one tricks me up. Thanks

What does it mean to say that Planck's constant is an energy oscillator composed of imaginary and real numbers? This is an expression I saw in a book.

Proof of kinetic energy work done equals a change in kinetic energy in a mechanical system. δW = F.ds W = ∫F.ds W = m∫a.ds W = m∫(dv/dt).ds W = m∫v.dv here if v and dv are in the same direction the change in kinetic energy will be the usual equation. what happens if both are in different...

I was taught to solve this problem by first finding the velocity of the body (of mass ##m ##) relative to the block of mass ##M ##. One way of doing this is as follows: first write $$ {v _{m _{B }}}^{2 }={v _{mx _{B }}}^{2 }+{v _{my }}^{2 } (I)...

I think the angular velocity keep increasing on the plane with friction and the translational velocity keep decreasing due to friction while the total kinetic energy is conserved. When it moves to the frictionless plane, all energy converts to translational kinetic energy and it stop rolling...

Can someone help me by taking a look at the attachment and figuring out where I am making a bad assumption? It's driving me nuts.

I've found some sound and not so sound answers so far. The most interesting is one saying that work is simply one form of energy. The answer used math to support it, but I haven't checked the math yet. Adult ADD, I believe, prompted me to move on instead. Maybe I just have no patience. Idk…

I initially thought about the different forms of energy present at each of the points: Total energy at starting point: PEA+ KEA= mgH at point D: KE_D = 1/2mv2f PED= mgD Energy at point D: PED+ KED D = mgD + 1/2 mv2f because EA= ED mgH = mgD = 1/2 mv2f mg(H-D) = 1/2 mv2f g(H-D) = 1/2...

It is known that while the electric current flows along the wire the energy propagates through the field near that wire (and not by means of electron gas kinetic energy) and the electrons' velocity is equal approximately to 10^[-3] m/s. Meanwhile, the electrons' velocity during the gas...

PF should keep up with the times https://www.livescience.com/planet-earth/nuclear-energy/physicists-solve-nuclear-fusion-mystery-with-mayonnaise :wink:

Q 1) In electric currents, in a battery, the positive charge starts at the negative terminal and gains energy through emf which forces the charge to go to the positive terminal of the battery, with plenty of energy. This voltage is the energy difference between the terminals. For the charges to...

>-Atomic orbitals must be at the similar energy levels to combine as molecular orbitals, said Wikipedia. This is unclear. How do you quantify how "similar" means? I heard electronegative is tied to atomic radius is tied to atomic orbital energy. What are two atoms that would in theory form...

I was doing a problem with this one detail. It says that the electric potential energy of an uniformly charged hollow sphere and a point charge is (at the surface of the hollow sphere; both positive): $$U = k \frac{q_1 q_2}{r}$$ I guess this assumes that the hollow sphere is a point charge. Now...

I'm only confused about one part of this problem and that is setting up the conservation of energy equation. In the solution, they just wrote this: $$\frac{mv_o^2}{2} = - k \frac{q_1 q}{r} + k \frac{q_2 q}{l + r}$$ where ##r## represents the distance at which the force created by the negative...

I am curious to know if there is any existing topic explaining how objects break into several pieces when force is applied.

So there was this question: The first option seems to be the only correct answer. $$\lambda_e=\dfrac{h}{\sqrt{2m(KE)}}$$. The answer would be correct if ##KE \approx eV## The option mentions that ##eV>>\phi## so ##\phi## can be ignored. But I don't think that necessarily means that the...

I used law of conservation of energy to calculate (d theta/ dt)^2 (from:mgasin theta=1/2m(d theta/dt.a)^2+1/2mu^2(u is the velocity of the C ring at time=t)), but wasnt able to find u(velocity of C).Is there any relationship between the tangential velocity of B(d theta/dt.a) and velocity of C(u)...

I thought the initial elastic potential energy would be converted to the arrow's kinetic energy but it also appears that the bow has some velocity.

For the first question I thought of using an energy balance, there is friction ##\Rightarrow \Delta E_m = -W_f##. Both at the start and at the end, the block has no velocity. Therefore ##E_{\text{initial}}= \frac 1 2 m_s v_{s,i}^2## and ##E_{\text{final}}= \frac 1 2 m_s v_{s,f}^2##. This means...

The pure energy coming from a collision and how is it measured or is it just "A Formula" and is any of that energy Dark Energy or even Dark Matter, the reason for the question is because the Dark Energy/Matter vs normal Energy/Matter seems to align with what is seen now after the Big Bang...

Hi, Can you please help me understand how the formula of energy decreasing during a sand leaking is obtained? One of possible solution to this problem, suggested in the textbook, states that when the bucket moves from x to x+dx (d is negative), there are two components responsible of energy...

For point one it's clear that I have to use energy => ##ΔE_{AB} = W_{friction}## ; ##\frac 1 2 mv_0^2 - \frac 1 2 mv_1^2 = mgμ_d d## After that there is the path BC, but I don't know how to analyze it from an energetic standpoint. Then after BC the block will now have a different velocity, I...

I tried to apply energy conservation . $$\frac{-kQq}{l}=\frac{m}{2}(v_1^2+v_2^2)-\frac{kqQ}{2r}$$ Now conserving momentum : $$0=mv_1-mv_2$$ Solving for ##v_1=v_2=v'## we get : $$v'=\sqrt{\frac{kQq}{m}\left(\frac{l-2r}{2r}\right)}$$ Since the balls are elastic , so they should collide...

R μν − 1/2g μν R= 8πG/c^4T μν In this formula, if the value of the energy momentum tensor(Tμν) becomes zero, can it become gravitational-free?

i got confused because if the connections btw the parts

If someone believes they have developed a somewhat unified theory that brings together various physics concepts into a Unified Theory of Energy, but they are concerned about being dismissed or criticized by members who strongly adhere to conventional academic views, where in the Physics Forum...

Can energy be stored in a single particle without it being lost over time? I mean, photons would be an exampld in principle, but they get redshifted as the universe expands and become less energetic as time goes by We could store that energy in form of kinetic energy for individual...

I understand every bond chemically has a length and energy to break, and energy is Newton*meters. Is the Bond enthaply/Bond disassociation energy equivalent to the force needed to break the bond * the bond length? Why don't we say, to break the bond from O to H we need to put magnets on left of...