Energy Definition and 999 Threads

Please redirect me to the correct part of thr forum if this is the wrong place When we lift up an object n then let it fall back, then potential energy - > kinetic energy If I drop a magnet onto another magnet with like pole facing each other (that sits on the floor), the falling one maybe...

There are n vertical identical parallel identical cilinders rotating around their length axes with the same angular velocity. The are somehow fixed wrt to Earth and brought together (on a rail?). After the contact there is no slipping and the cilinders are coupled to their neighbor cilinders. It...

This is a 3D model I made of a large industrial steam turbine. It was modeled after one of the turbines at the Port Richmond generating station in Philadelphia Pennsylvania. I plan on modeling the entire turbine hall of that power plant, but that will take several months, at least. The program...

Please excuse my physics ignorance. Can usable energy be extracted from alpha particles? Perhaps in a manner similar to a photovoltaic panel producing power when exposed to light? Thank you.

I used the Change in Kinetic Energy and equated that with the Work Done. The "Work Done" part comprises of two different functions- one is work done by Gravitational Force while the other is the work done by frictional force (or the brakes). /Delta KE (magnitude wise)= 0.5*1350* (20^2)=270,000...

Solution 1: Force on air = Force on helicopter. ##F = \frac {dp} {dt} = v \frac {dm} {dt} = v^2 \rho A## ##P = Fv = \rho A v^3## Solution 2: Power from helicopter converted to rate of kinetic energy increase of air ##P = \frac {dE} {dt} = \frac {1} {2} v^2 \frac {dm} {dt} = \frac 1 2 \rho A...

> The set up: At left end, the rope is pulled down with a distance $dx_1$ by a force of constant magnitude $F$, the mass of $M$ is wrapping around by rope on the right and moves up by a distance $dx_2$ due to this. Problem: Find relate the two displacements. I thought of applying energy...

Are the typical energies of virtual particles lower than real particles?

I understand that potential energies are energies relative to reference points. For example, gravitational/electrical potential energy is relative to a point at infinity. What is the reference point for centrifugal potential energies? In the case of planetary orbits, must the reference point...

While physics is generally believed to be CPT symmetric, there are processes for which such symmetry is being questioned - especially the measurement. One of examples of (allegedly?) going out of QM unitary evolution is atom deexcitation - we can save its reversibility by remembering about...

I want to study strain effects on the one material which has non-zero on-site energy . Does strain affects on-site energies?

I thought the first step is to compute the loss of mass. ##\Delta m=m(_1^2\textrm{H})+m(_1^3\textrm{H})-m(_2^4\textrm{He})-m(_0^1\textrm{n})=2.0141018u+3.0160493u- 4.0026033u-1.0086650u=0.0188828u##. The corresponding reaction energy is ##0.0188828 \cdot 931,5MeV=17.54MeV\approx 2.81\cdot...

The equation below allows us to calculate the potential energy of a continuous distribution of electric charge. $$U=\frac {\epsilon_0} 2 \iiint\limits_\text{Entire electric field}\vec E^2\,dV$$ In my textbook, the author states $$U=\frac 1 {8\pi\epsilon_0}\iiint\limits_\text{Entire electric...

Generally, one would expect the beam to lose its content (energy or particles) if it hits anything before its reaching its target. The whole idea of maintaining (conventional) vacuum using pumps or other means is to minimize that loss. But is it possible that there could be a beam loss purely...

Also, I have heard from physicists that vacuum energy fluctuation (creation and destruction of virtual particles) violates energy conservation. The reason, they justify, is based on uncertainty principle (energy-time form of uncertainty principle), energy can exist and disappear for a very short...

So we all know that the form of the momentum operator is: iħd/dx. And for energy it is iħd/dt. But how do we derive these operators? The only derivations of the i have seen is where the schrødinger equation was used, but that makes the logic circular, because the Schrødinger-Equation is derived...

Molecular potential energy of hydrogen in dependence with atomic distance for bonding orbital is given by picture below. We can see that at large distances force between atoms is attractive and potential energy drops to minimum which corresponds to bond energy and length. This part of the...

Toughness is defined as ability of material to absorb energy when deforming before fracture. Materials with high ductility and strength will have high toughness. What is meant by ability of material to absorb energy? What is connection between strength, ductility and ability to absorb energy so...

Hi. Anybody every wondered why we pay to run dehumidifiers in cold climates, when so much moisture could be condensed through the use of outside air temperature/transfer ..ie look at the condensation on your windows ! ...(summer months ...open a window or just circulate outside air). Of course...

Explanation 1: Eddy currents induced, energy loss due to joule heating. Explanation 2: Eddy currents induced, induced magnetic dipole formed. Energy is lost as work has to be done to overcome the attractive/repulsive force due to the magnet and the induced magnetic dipole from the eddy...

Hi! After watching a couple videos about the explosive reaction of sodium in freshwater and seawater, I felt curious and wanted to calculate how much energy is released. However, my Chemistry is super rusty and I think that my result is way too high (equivalent to almost 2 g of TNT per gram of...

Particle X of mass 2 kg , and particle Y of mass m kg are attached to the ends of a light inextensible string of length 4.8m. The string passes over a fixed smooth pulley and hangs vertically either side of the pulley. Particle X is held at ground level, 3m below the pulley. Particle X is...

i found current to be 2/5 A. then 2/5A multipled by 6s = 2.4C. and since one joule per coulomb is equal to the unit of p.d, i get 2.4J. I don't get 4.8J(supposed answer)

Can the energy-momentum tensor of matter and energy be cast in terms of energy density of matter and energy, similar to how the energy-momentum tensor of vacuum energy can be cast in terms of the energy density of vacuum energy?

From hyperphysics, "The unique point in the case of the traveling wave in the string is the element of the string that is at the maximum displacement as the wave passes. That element has a zero instantaneous velocity perpendicular to the straight string configuration, and as the wave goes "over...

A car of mass 1200 kg accelerates up a hill inclined at 10 degree to the horizontal. The car has initial speed of 10 m/ s and final speed of 12 m/s after 60 s. Air resistance and friction may be ignored. Find the average power generated by the engine. The and in the textbook is 36000 W, iam...

Suppose I am sliding a block very slowly on a rough surface. If the block has traveled ##d## distance then work done by me is ##W_1=\mu mg d## and that by friction is ##W_2=-\mu mg d##. Now the energy transferred from me to block is ##\mu mgd## and that taken by friction from block is ##\mu mgd...

I don't need equations, I would just like to pose a question which contradicts the above statement (I know I am wrong btw, I want to see where I am going wrong).My understanding of space (not near any gravity and therefore no spacetime curvature) is that a body in motion will continue to move at...

A golf ball of mass 45.9g is hit from a tee with speed 180km/ h. The ball rises to a height of 20m having traveled along a curved path of length 61.875m. At the highest point of its path the ball is traveling at 144 km/h a) Find the magnitude of the avg resistance force acting on the golf ball...

Hi Guys ! Previous question was to determine the energy of photon with wavelength = 820nm I found that E = 2.42x10^-19 J = 1.51 ev using the equation E=hc/wavelength - I tried to solve the above problem with various equations but all failed. The closest equation i tried is...

Earth absorbs and releases a massive amount of energy as a part of the day night cycles.(~100 Peta watts of solar radiation received) And the temperature difference between the poles and equator drive weather phenomenon, which happens at an energy scale beyond technology. I am wondering if one...

A golf ball of mass 45.9g is hit from a tee with speed 50 m/ s. The ball lands in a pond 5m lower than the tee. When the ball lands in the pond it has traveled a curved path of length 160m. The resistance acting on the ball has magnitude 0.3N a) Find the speed of the ball just before it hits the...

A sky diver of mass 80 kg falls 1000m from rest and then opens his parachute for the remaining 2000m of his fall. Air resistance is negligible until the parachute opens. The sky diver is traveling at 5 m/ s just before he hits the ground. Find the average resistance force when the sky diver is...

Quantum mechanically, a spin 1/2 particle in a uniform magnetic field has two energy eigenstates ##\ket{up}## and ##\ket{down}## and rotational degrees of freedom (distinct from the energy eigenstates) about the axis of the magnetic field. this can be derived from the Pauli matrix commonly...

A football is kicked from the ground level with speed 15m/s and rises to a height of 1.45m. Assume that air resistance is negligible a) Find the speed of the ball when it is 1m above the ground Increase in GPE= loss of KE mgh=1/2mu^2-1/2mv2 10×(1.45-1)= 1/2×15^2-v^2/2 V= 14.7 m/ s But textbook...

A box slides down a smooth ramp. The height of the ramp is 20cm and the length of the ramp is 2.5m. The box starts from rest. What is the speed of the box when it reaches the bottom of the ramp? I don't understand how to solve this. Pls help

The ##I_i## are the intensity of the rays, in other words energy per surface units per radians by seconds. The d##\Omega## are the solid angles The equation p75 isis what I don't understand. I suppose that each side represent the energy going and out of the surface dS but I don't understand...

Hello, I have a particle at point A with charge ##q_A##, and an unmovable sphere of radius ##R_B## at point B with a volumic charge density ##\rho##. The distance from particle A to the centre of the sphere in B is ##r##. Both objects have opposed charges, so, the particle in A, initially at...

A child of mass 40kg slides down a playground slide. The child starts from rest at the top of the slide, 2m above the ground. At the bottom of the slide it's slope levels off. a) Find the child's loss of GPE I got the ans 800J there is a constant resistance of 112N throughout b) find the...

A girl of mass 50 kg travels down a water slide. She starts at the top with a speed of 2 m/s and descends through a vertical height of 5m. a) Assuming that there is no resistance, find her speed when she reaches the bottom of the slide I got the ans 10.2m/ s b) the girl's actual final speed is...

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?