Total energy Definition and 221 Threads

I'm working on a homework problem which states: "Some object, starting from far down the negative x-axis and moving in the positive x direction, experiences a force, the potential energy U of which is modeled by the function U = 2e^(-x^2), where x is in meters and U is in Joules. The total...

Homework Statement This isn't a math problem but just a vocab question, what is the total energy of a system called? Homework EquationsThe Attempt at a Solution In the physics textbook by resnick and halliday, they define mechanical energy of a system as the energy of a certain Configuration...

Homework Statement If two satellites A and B are orbiting the Earth out of which A is closer to the Earth then the total energy of which Earth plus satellite system is lesser?Homework EquationsThe Attempt at a Solution Should I consider only the magnitude while comparing using the formula total...

Homework Statement This is not really a homework questions, just part of my notes confusing me a bit. This is the derivation of total energy for a pendulum of mass m2 with movable pivot of mass m1. I don't understand how frequency can be read off. What am I missing? Homework Equations See...

Homework Statement So a little background before stating the problem: During a lecture a couple weeks prior to lab, the instructor did an example where we were told to find the max height of a ball launched upwards by compressing a spring. In order to calculate that, he showed that E1 is the...

Hello guys, I am developing a physics system that simulates collision between two cubes. I need to calculate the total energy in those cubes in an instant before the collision. I know that the total kinetic energy in this case is the sum of the angular velocity energy and the linear velocity...

Homework Statement A mass of 20kg is suspended at a high of 5 meters above the ground. It is on the moon (then acceleration = 1.635 m/ss). It falls, and we want to know the total energy halfway, at 2.5 meters above the ground. Homework Equations I suppose the equations I need to use are...

hey guys, I am trying to find the effect of friction on the total Energy of an object my object is a small car with 2 motors with a known speed and a constant one (without an acceleration) this object will be dragging a certain mass behind it I already came out with an equation but not...

Homework Statement Consider the charging capacitor in problem 7.34 (A fat wire, radius a, carries a constant current I, uniformly distributed over its cross section. A narrow gap of wire, of width w, w<<a, forms a parallel-plate capacitor) a) Find the electric and magnetic fields in the gap, as...

Homework Statement If height of a satellite from the surface of Earth is increased, why does the total energy increase? Homework Equations T.E=K.E + P.E The Attempt at a Solution Here the work done by non-conservative forces is zero. This means that the total mechanical energy of the system...

Homework Statement An electron in a very thin wire of length L= 1 nm (10-9 m) can be modeled as a particle in an infinite box. Solve for total energy using boundary conditions at L 2. The attempt at a solution WaveFunction -- > PSI = A Sin ( kx ) ; k = n*pi/L ; A = sqrt(2/L) "After...

I posted recently on a banned topic, apologies for that. Under advisement of a mentor I've decided to ask a positive question instead, how do scientists estimate the total energy of the universe?"

Homework Statement When an initially charged capacitor is connected in a circuit with an uncharged capacitor, why would the total energy of both capacitors be less than the initial energy of the charged capacitor? Homework Equations This was a question asking for an explanation, so I'm not...

Hello! So this is a rather stupid question, but I'm having trouble with gravitational fields, and can't exactly pinpoint what's going on. The total energy of an orbiting satellite is (due to ME = KE + GPE) (-GMm/2r), right? Well, I have found multiple statements that claim that the 'r' we use...

Homework Statement The problem asks me to find the expectation value of W. Homework Equations The given ψ[x,t] is Asin(πx/a) e^((-i Eot)/ħ). By QM postulate 2 the QM operator of W is: iħ δ/δt or equivalently -ħ/i δ/δt. The Attempt at a Solution <w>=∫ψ*iħδ/δtψ= iħδ/δt 1/(2e^(-iEot/)ħ)...

Homework Statement The position of a 50 g oscillating mass is given by x(t)=(2.0cm)cos(10t−π/4), where t is in s. If necessary, round your answers to three significant figures. Determine: The total energy. Homework Equations T = 2π/w T = 2π√m/k 1/2kA^2 1/2mv^2 1/2kx^2 The Attempt at a Solution...

If a ball rolls in a semicircular track starting from one end of track,( the track is kept vertical) and if radius of ball is r and radius of track is R is this expression correct? (When ball reaches lowest point) ##mg(R-r)=\frac{1}{2}I_0\omega^2 + \frac{1} {2}I\omega_1^2+\frac{1}{2}mv^2## where...

Hi, Sorry if this is a totally idiotic question, but I was wondering how you can calculate the energy of an electron as the temperature of the surrounding environment is changed. Thanks so much!

Homework Statement a.) Find the total energy of vibration of a string of length L, fixed at both ends, oscillating in its nth characteristic mode with an amplitude A. The tension in the string is T and its total mass is M. (HINT: consider the integrated kinetic energy at the instant when the...

Can someone provide for me a proof that the total energy of my equivalent capacitor is equal to the sum of the energy in all capacitors? Or, if this is untrue, tell me why? Is this applicable to current and resistors too? Thanks a lot.

According to the schematic (FIG 1) in this paper (http://journals.aps.org/prb/abstract/10.1103/PhysRevB.80.085202) the total energy of a solid with N+1 electrons is less (more negative) than the same solid (the same positions of ions) with N electrons. This was explicitly shown for the single...

A simple harmonic oscillator has total energy E= ½ K A^2 Where A is the amplitude of oscillation.  E= KE+PE a) Determine the kinetic and potential energies when the displacement is one half the amplitude. b) For what value of the displacement does the kinetic energy equal the potential...

Homework Statement A block of mass 0.25 kg is connected to a spring with spring constant 35 N/m. The block is oscillating on a frictionless horizontal surface. Its speed as it passes through its equilibrium position is 1.04 m/s. What's the total energy of the system?2. The attempt at a...

Hi, I am working through Carrol's book on General Relativity. On page 206, he makes the following statement: How does this follow from the definition of a Killing vector? He uses this equation to determine the total energy (equation 5.61). Thanks in advance. EDIT: This makes sense for a...

I have a question about the derivation that I have attached! I understand that both KE and U are 1/2 kA^2 So how is it that the two combine is also equal to 1/2kA^2Not sure if I'm missing something but I'm a little confused :(

Homework Statement Hi, my question is regardng a Coulomb model of an H atom specified with Hamiltonian operator, Hhat, by spherical coordinates of energy eigenfunction ψ2,1,-1 (r,θ, ∅) =(1/ 64∏a02)1/2 r/a0 e-r/2a0 sinθ e-iθ Principal quantum numer n = 2 orbital an mom l = 1 magnetic...

I'm kind of new to special relativity, I mean beyond what they tell you in survey courses. In any case, I've heard there was a relationship between energy and time in special relativity (I've actually heard someone say the "time component" of energy), and I've always been fascinated with E = mc2...

http://s9.postimg.org/vejo37agv/physics.jpg for picture Asteroids X, Y, Z have equal mass (6kg each). They orbit around a planet with M=6×1024kg. The orbits are in the plane of the paper and are drawn to scale. TE, KE and PE represent Total, Kinetic and Potential energies. Select G-Greater...

Suppose we've got two still particles of any mass we would like, infinitely far apart. The total energy here is of course sum of their mass energies. Now if we bring them together so that one orbits around the other, what would be the total energy of this system? Perhaps, my guess, in such...

Homework Statement A two-dimensional water wave spreads in circular ripples. Show that the amplitude A at a distance R from the initial disturbance is proportional to 1/\sqrt{R} Hint: Consider the energy carried by one outward moving ripple Homework Equations Kinetic energy carried by...

Okay, so if a harmonic oscillator has a restoring force given by Hooke's Law such that Fs = -kx and its integral gives the potential energy associated with the restoring force: PE = -(1/2)kx2 Then for the total energy of a harmonic oscillator, why is the TE: TE = Evibration +...

Homework Statement A car of mass 850 kg is driven at a steady speed of 70 km/hr up a hilly road with a slope of 30°. Using the macroscopic energy equation, determine the power delivered by the engine of the car. Homework Equations E= KE + PE E = (1/2)mC^(2) + mgz Power = E/t...

Homework Statement one capacitor is charged until its stored energy is 4.0 J, the charging battery then being removed. a second uncharged capacitor is then connected to it in parallel. if the charge distributes equally what is now the total energy stored in the electric fields? where the...

Total energy when positions vs time graph is given Homework Statement (answer: -5J) Homework Equations energy initial = energy final The Attempt at a Solution At the crest of each wave, the particle has only potential energy, and at the middle of each wave the particle has only...

I know total energy is conserved, but does this mean that different frames agree on the total energy of a particle? I'm assuming they don't agree on energy, because if I measured the total energy of a particle moving relative to me (which would equal the rest energy plus its kinetic energy)...

Homework Statement Had to work out the total energy in a mass spring system (Part d of question), which has been found to be: (v^2*m/4)[sin^2(nt) + sin^2(3nt)] The next part of the question (e) says to 'Discuss the meaning of your result to part (d) above' And I have no idea what to...

The KE (kinetic energy) of an electron revolving around a nucleus is always positive, and the PE (potential energy) of an electron is negative (except at infinity, where it is zero). Here, I am speaking from the point of view of the Rutherford model. The material from which I am reading from...

I was thinking about the following thing: we know that if the Lagrangian in field theory doesn't depend on the spacetime position, the Noether's theorem says that the stress-energy tensor is conserved, and that T^00 is the energy density at spacetime point x. Then if one integrates this h(x)...

In the picture to the left they're summing up the potential energies but I don't understand why they equal to (Q^2)/2C. Almost like both of them put together is like a giant capacitor? Not sure how they got this any help would be appreciated. This is coming from the book University Physics 13e...

Its stated that total energy of an isolated system is given by E = \frac{1}{2}mv^{2} + \frac{1}{2}Iω^{2} + mgh. Whats the correct form when the velocity is along 2 axis, that is, along x and y-axis like v = (2, 1)? Should the resultant be taken or just add the kinetic energies along each axis...

Hi, the gravitational field around a black hole is a form of negative energy. When a black hole evaporates it is converted into photons. These photons move away from the black hole. After it evaporated the gravitational field is gone so the negative energy is gone. But the total amount of...

hi, 1- if the universe total energy is zero, is this mean that the universe can come from (zero energy + zero energy = 0 ) to (negative energy + positive energy = 0 ) 2- if in a system of the total energy is (E - E = 0) does the conservation of energy allow a system to change to (2E...

Homework Statement We have an object whose mass is 0.7 kg moves with an equation y=0.45cos8.4t. Find the general energy w=8.4 A=0.45 Homework Equations E=mv^2/2 +kA^2/2 The Attempt at a Solution So I found k using w=(k/m)^0.5. And then I found V0 using V0=A*(k/m)^0.5 and...

Homework Statement A 200 kg boulder falls from rest off a 120.0 m high cliff. If the boulder experiences a frictional force of 280 N[U] as it falls, what would be the velocity just before it hits the ground? Homework Equations kinetic energy = (1/2)mv2 gravitational potential energy =...

Given a cylindrical wire of radius r, length L, carrying a current I, find the total energy stored inside the wire. From griffiths, uem= εE2/2 +B2/2μ and the tot energy is ∫uem dV I have my E and B fields, but my B field is a function of x where x<r, (E is uniform) B=kx/r2...

Assume that we have a particle i at rest according to co-moving coordinates. Then the total energy of the particle at rest, E_i, is its rest mass energy plus the sum of the (negative) gravitational potential energies between it and every other particle in the Universe. Thus we have \large...

Homework Statement A particle, observed in a particular reference frame, has a total energy of 10GeV and a momentum of 6GeV. What is its mass in units of GeV/c^2?Homework Equations I used p=\gamma mv and E=\gamma mc^2The Attempt at a Solution So I divided the above equation for P by the...

Homework Statement The problem I am doing is problem 1.55 in Schroeders Intro to Thermal Physics. Unfortunately, I have to come here for help a lot because the office hourse are not until after the homework is due...In any case, the first part of the question was to show that the potential...

Homework Statement Calculate the total energy of a geosynchronous satellite (one that orbits over a fixed spot) with a mass of 1.5 x 10^3 kg, orbiting Earth st a height of 325 km with an orbital speed of 5.0 x 10^3 m/s. Homework Equations Ek = 1/2 mv^2 Ep = mgh Fg = Gm1m2/r^2 or PE...

I'm confused as to what scientists agree on, since I've read many answers. Is the total energy of the universe less than, equal to, or greater than zero? Is the universe open, flat, or closed? (I'm not sure if this is the exact same question as the previous) Is this a debate within the...