Energy Definition and 999 Threads

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...

I tried to take angles and proceed by energy conservation But this doesn't seem to lead me anywhere . Here , the length of threads is ##l## each and ##2\theta## is the central angle. ##y_1## is the displacement of the charges attached at the extreme ends of the threads respectively while ##y##...

TL;DR Summary: does the quantity we refer to as energy actually exist energy is a property of a physical system but does it actually exist, like does an object actually lose or gain a quantity that we refer to as energy after an interaction, or is it just a mathematical concept, are those...

Source: Shankar Yale OCW physics I have three questions here: 1. K_avg is 3/2kT, sure. But isn't this the kinetic energy of one particle only? So why isn't the answer multiplied by avogadro's number (because one mole). 2. When doing the "typical velocity" derivation, I noticed that they used...

Attempt: I assume that the position of the mass ##M## after it is realised its position is given by the position vectors from the origin, ##\vec m = -m(t)~\hat m## if ##m(t) > 0## or equivalently ##\vec m = m(t)~\hat m## if ##m(t) < 0## Either one we can use for energy conservation (I am...

I am reading A. P. French's book: "Special Relativity". Currently I am focused on the section: "Matter and Radiation: The Inertia of Energy." Under the heading: "Matter and Radiation: The Inertia of Energy", French writes the following: In the above text by Young...

Hi, I've been asking questions about light here for years, and I still don't understand the limit of propagation of light, does anyone have advanced on this field? I really would like someone to explain me how it's possible for light to propagate forever, since it's probably emitted in perfect...

Is it theoretically possible for the expansion of the universe to red-shift the energy of a photon all the way to zero? If so, what happens to the photon? Or does the photon's energy only approach zero as an asymptote?

Hello community, I am currently designing a gravity-based electricity generator and exploring the feasibility of different setups using a 500 kg mass. The core of my project is to harness the potential energy from this mass as it is lowered from a significant height. I am considering several...

Kinetic energy = 1/2 m V^2 I was thinking about this and thought another formula… E = mc^2 These look very similar except for the multiplication by 1/2. Let’s say you take a kilogram ball of uranium and accelerate it to the speed of light. I know, I know. You can’t. But let’s say you did...

1/ Have a closed hydraulic circuit. Two columns of fluid. One hot, one cold, which are connected at the bottom and top. Let's have small heat loss and small hydrodynamic resistance to fluid flow and incompressible fluid. I heat the lower interconnection, I cool the upper interconnection. I have...

How can i calculate the Energy required to bring 1 kg 1000 meter above the surface of the earth ?

from what I understand, work is the integral of the force with respect to displacement along the path of displacement $$\Delta w=f*\Delta r$$ and is defined so that the change in kinetic energy is the work, as for potential energy it is the work done to change the position of the object from...

A charged, metallic box has an energy content higher than an uncharged box, due to the energy stored in the electric field (which is equal to the work that has to be done to bring the charges from "infinity" to the surface of the box). So, due to the mass-energy equivalence, a charge box has a...

I am going to use this coordinate system: According to the answer of the book, I think no force is acting on this projectile: Let's say at top of it's trajectory its velocity is ##u##. Conservation of energy : $$2E_0=\frac 1 2 m_1 v_1^2+\frac 1 2 m_2 v_2^2$$ Conservation of momentum in...

It is said that the universe is made up of approximately 4.9% ordinary matter, 26.8% dark matter and 69.3% dark energy. Why isn't ordinary energy included in this "pie"? I suppose it is included within ordinary matter, but could it be calculated what % are particles with mass and what % is pure...

This is what I have for my solution thus far: "For gold to transition to mercury, it must exchange one of it's neutrons for a proton via ##\beta##-decay. In order to find the energy of the emitted gamma rays, we must first find the excess rest energy ##Q## present after the ##\beta##-decay. The...

In order to change the radius, additional energy is required, the total energy of mass m on a circular orbit is given by: $$E_{total} = - \frac {GMm} {2R},$$ The change in energy between orbits ##R## and ##R_{0}## is: $$\Delta E_{total} = \frac {GMm} {2} \cdot \left( \frac 1 R_{0} - \frac 1 R...

I attempted the problem by first finding the radial, theta, and phi equation for the ground state of a hydrogen atom. I multiplied the three equations to get the wave equation. From there, I took each derivative in the Schrodinger Spherical equation and found that ## \frac {\partial^2 \psi}...

Is it possible to move Stress-Energy tensor to the left side of EFE? R=T => R-T=0. Relativists move cosmological constant Λ to the right side of EFE. Can we move SE tensor to make a vacuum?

I believe that when a photon is refracted it slows. Why is it that the wavelength decreases but that its frequency stays constant? Does this imply that the photon has not lost any energy in the process of slowing down given that E=hf? Thanks

I believe that when a photon is refracted it slows. Why is it that the wavelength decreases but that its frequency stays constant? Does this imply that the photon has not lost any energy in the process of slowing down given that E=hf? Thanks

I was watching this YouTube video by the channel The Action Lab: At one point it shows this capillary tube phenomenon: It got me immediately thinking: Conservation of energy much? What's stopping that second tube from being bent into draining into the leftmost tube, thus creating an...

Hi, so this is a lab in which we used an air track at an angle and a glider to gather some data through various trials, ultimately to calculate "g". L_glider = 10.15 cm x (photogate activation point) = 547.5 mm or 54.75 cm x_0 (release point) = 1800.0 mm or 180.00 cm (Δx)_midpoint = | x - x_0 |...

I did some algebra and got the final equation mgh=1/2MR^2omega^2+1/2(2/5MR^2)omega^2, then plugged in the numbers and got an omega value of 111.09. Using 1.7 as h instead of cos(17)*1.7=1.63 I got 114.09. Both answers were wrong. Am I missing something, or did I just screw up the math?