# What is Total energy: Definition and 232 Discussions

In physics, energy is the quantitative property that must be transferred to a body or physical system to perform work on the body, or to heat it. Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement in the International System of Units (SI) of energy is the joule, which is the energy transferred to an object by the work of moving it a distance of one metre against a force of one newton.
Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature.
Mass and energy are closely related. Due to mass–energy equivalence, any object that has mass when stationary (called rest mass) also has an equivalent amount of energy whose form is called rest energy, and any additional energy (of any form) acquired by the object above that rest energy will increase the object's total mass just as it increases its total energy. For example, after heating an object, its increase in energy could be measured as a small increase in mass, with a sensitive enough scale.
Living organisms require energy to stay alive, such as the energy humans get from food. Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy. The processes of Earth's climate and ecosystem are driven by the radiant energy Earth receives from the Sun and the geothermal energy contained within the earth.

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1. ### I Car, gas and total energy calculation

Hi, What I understood about the principle of conservation of energy: Et = Ep + Ec = constant. For example: Et = 1/2mv^2 + mgh (h = height). Consider a car moving at speed v. For example: Et = 1/2mv^2 + E(gas + exhausts). Indeed, I include the exhausts, otherwise with the drop in the quantity...
2. ### Kinetic Energy / Potential Energy / Total Energy question

W_ext is the external work done on B and C, which is 12 J Delta K_tot is the internal work, which is the work done by A on B plus the work done by A on C Delta K_tot = 5 Solving for \Delta U, we find that the change in potential energy is 7 J This answer says otherwise...
3. ### Calculate the total energy required to fly a drone on this flight plan

How much energy will drone batteries will consume if I have the following inputs, By using provided GPS flight path data I've calculated total horizontal distance using Haversine formula, and multiplying this distance with provided horizantal speed I've total horizontal flying time. By...
4. ### Total energy of a mass hanging on a spring

Hello! So here what I did is first calculated the potential energy; $$E_p = \frac{1}{2} * k * x^2$$ E_p should be = 0,125 J Now i tried calculating the kinetic energy, I used this formula $$E_k = \frac{mv^2}{2}$$ to get v I used this formula $$v = x *\sqrt{\frac{k}{m}}$$ v should be =...
5. ### Redshift & Total Energy Density

1. If today vacuum and matter contribute 71 % and 29 % to the total energy density of the universe, at what redshift z were they contributing equally? 2. If today vacuum, matter, and radiation contribute 71 %, 29 %, and 0.01% to the total energy density of the universe, at what redshift z were...
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### B Calculating the Total Energy of a lattice w/ the Madelung constant

For an ionic lattice, the contribution to the electric potential energy from a single ion will be ##U_i = \sum_{j\neq i} U_{ij}##, which can be expressed as\begin{align*}U_i &= -6 \left( \frac{z_+ z_- e^2}{4\pi \varepsilon_0 r_0} \right) + 12 \left( \frac{z_+ z_- e^2}{4\pi \varepsilon_0...
7. ### Total energy of the normal mode on a string

What you think about this question? Seems a little strange to me, that is, it considers the maximum kinetic energy when the displacement of the oscillators is maximum, i don't think this is right.
8. ### I Normal modes of vibration from the total energy

A mass ##m## is restricted to move in the parabola ##y=ax^2##, with ##a>0##. Another mass ##M## is hanging from this first mass using a spring with constant ##k## and natural lenghth ##l_0##. The spring is restricted to be in vertical position always. The coordinates for the system are ##x##...
9. ### I The total energy stored in a battery (theory/formula)

What's the total energy stored in a battery that can be expended in a circuit until it's depleted?
10. ### I Total energy of an isolated system

If a closed system has kinetic and potential energy such as the total energy (the sum of the two) equals zero for all times, what does that mean? In other words, what does it physically mean that the total energy is always zero for a closed system? I think I have a small misunderstanding of the...

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### B Contributions to total energy in different areas of Physics

Classically, the total energy of a particle/system ##E = T+V##. This is the usage seen in the Schrödinger equation, since E is an eigenvalue of ##\hat{H}## and ##\hat{H} = \hat{T} + \hat{V}##. Then in special relativity, the total energy ##E## of a particle/system becomes the rest energy plus...
13. ### The Total Energy of the Hydrogen Atom's Electron

Homework Statement:: The total energy of the electron in a hydrogen atom is normally −13.6 eV. Which one statement below, based on this fact, is correct? 1. The work required to completely remove the electron from the atom is 13.6 eV. 2. The electron is in a circular orbit with a kinetic energy...
14. ### Find the Total Energy of the String

Steps that I've taken: First, compute the derivative of the psi-function with respect to time and then take the square of the result Second, input the result into the KE integration formula. All that is left is to find the integrand, however this is where calculations became really "messy". It...
15. ### I Derivation of the conservation of total energy and momentum

I want to derive from ##T^{\mu \nu}_{,\nu}=0## the equation: ##\int T_{0\mu}d^3 y=constant##, I don't see how exactly. From the derivative I know that ##T^{0\mu}_{,\mu}=0##, but I don't see how to integrate this equation, it's ##T^{00}_0+T^{0i}_i=0##. But how to proceed from here? Thanks in...
16. ### I Is the total energy of the observable universe constant?

If so, do we have estimates of what that is. Also, if we have estimates of that, what will the final entropy of the universe be, in J/K?
17. ### Total energy of hydrogen at ground state

Homework Statement What is the total energy of the hydrogen atom at ground state? a. 13.6 eV b. mpc2 + mnc2 c. mpc2 + mnc2 - 13.6 eV d. mpc2 + mnc2 + 13.6 eV Homework Equations E =...
18. ### Python: Simulation of the Solar System and Total energy

Homework Statement I have a project to make the Solar system on Python, which I have done, but they also require from us to calculate the total energy of the system. We don't have to make the orbits of the planets elliptical, they should be circular and I believe I made them like that. Since...
19. ### I How to estimate total energy when dealing with beamsplitters

I'm having a brain freeze right now and I need some help. :frown: I have a 50/50 beamsplitter (non-polarizing) with 5% tolerance. Test measurement (with a laser at a certain wavelength) gave that I'm transmitting 5.36 units and reflecting 4.6 units (49.5 transmitted; 42.6% reflected). Units...
20. ### Calculating Total Energy with Dimensional Analysis | Screenshot Included

Homework Statement Please look at the screenshot. Homework Equations dimensional analysis The Attempt at a Solution Since the heat capacity is given as 11.3 kJ/(C*g), and energy is measured in Joules (or kJ), I thought to multiply 11.3 by the change in temp (7.3 C) and also 1.50 g of...
21. ### Given force as a function of x, how do I find the total energy?

Homework Statement F=-kx+kx3/α2 where k and α are constants and k > 0. Determine U(x) and discuss the motion. What happens when E=kα2/4? Homework Equations F=ma=mv2d/dx U=-∫Fdx The Attempt at a Solution The first part is easy. U(x) = kx2/2-kx4/4α2 Now I'm looking for what happens when E=kα2/4...
22. ### Total energy (ETOTAL) is not zero and increasing (Abaqus)?

Hi all, I have performed a small static analysis with one element (C3D8). The bottom face of element is completely constrained, and the top part is displaced. In the geometrical linear analysis, the internal energy (ALLIE) and the work done (ALLWK) are equal. So, with ETOTAL = ALLIE - ALLWK...
23. ### Laplacian in spherical coordinates

Homework Statement Hello at all! I have to calculate total energy for a nucleons system by equation: ##E_{tot}=\frac{1}{2}\sum_j(t_{jj}+\epsilon_j)## with ##\epsilon_j## eigenvalues and: ##t_{jj}=\int \psi_j^*(\frac{\hbar^2}{2m}\triangledown^2)\psi_j dr## My question is: if I'm in...
24. ### Total energy of a body in a circular orbit

Homework Statement Homework Equations The Attempt at a Solution Is the particle moving under the influence of a single central force ? Since the force always acts towards the center , work done by the force is zero . Energy is conserved . Potential energy at a particular radius can be...
25. ### How Does Total Energy Relate to Potential Energy in a Closed System?

Homework Statement Why is it that when the total energy of a system less than the max potential energy, it must equal to some potential energy in a potential energy diagram. Homework EquationsThe Attempt at a Solution Total energy intersects multiple points in U(x) diagram. However, since...
26. ### I Hamiltonian in Schrödinger: necessarily total energy?

This is a basic question, so probably easy to answer. The following from Wikipedia seems pretty standard while describing the Schrödinger equation: "...and Ĥ is the Hamiltonian operator (which characterises the total energy of the system under consideration)." On the other hand, from page 100 of...
27. ### Finding the total energy of a Pi meson

Homework Statement A K meson (an elementary particle with approximately 500 Mev rest mass) traveling through the laboratory breaks up into two Pi mesons (elementary particles with 140 Mev rest energies). One of the Pi mesons is left at rest. What is the total energy of the remaining Pi meson...
28. ### Total energy of charge in parallel plate capacitor

Homework Statement Find the total amount of energy of a charge (q) initially at rest placed at the left plate of a parallel plate capacitor. The left plate is at V = 0, the right plate at V = V0 and the plates are a distance L apart. Homework Equations Etot = 1/2 mv2 + qφ(x). φ(x) = Vx/L The...
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### How to calculate the total energy in the point given.

Homework Statement The question wants the total energy of point A. Point A is 35 m above the ground and the mass of the objecy is 150 kg. The velocity is 10m/s. (And point B is 20 m above the ground and point c is 26.) Homework Equations Ek= 1/2*mv^(2) Ep=mgh Total= Ek+Ep But for some reasons...
30. ### I Hamiltonian as total energy for natural systems?

Could someone please prove that the H=T+V for systems where the transformation from Cartesian to Generalized coordinates is time independent. I have read through the proofs in Taylor's classical mechanics and Goldstein's but do not understand them.
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### SHM and Total Energy Equations for Solving Homework Problems

Homework Statement Homework EquationsThe Attempt at a Solution KE=1/2mω2x2 doesn't this mean is it proportional to all A.B.C&D? Thank you!
32. ### A Deriving total energy in a Hydrogen molecule

I am looking for litterature that derives mathematically the total energy in a ##H_2## molecule by using quantum physics. Anyone knows a book they can recommend. I have seen derivations for helium atom for example: http://farside.ph.utexas.edu/teaching/qmech/Quantum/node128.html I need...
33. ### Total energy of a shell charge

Suppose a spherical shell is kept at the orgin. Its surface charge density is ##\sigma## and radius is ##R##. I think I remember the formula for its electric potential energy is ##U = \displaystyle {Q^2 \over 2R}##. Now I want to derive it. I used ##\displaystyle U...
34. ### Total energy within a specific region.

Homework Statement A cubical region 1.0 m on a side is located between x=0 and x=1 m. The region contains an electric field whose magnitude varies with x but is independent of y and z: E=E0(x/x0), where E0 = 32 kV/m and x0 = 6.0 m . The answer needs to be in μ J. Find the total energy in this...
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### Calculate total energy surface tension

Homework Statement Consider a planar liquid-gas interface and a solid sphere partially immersed in liquid. A fraction of the solid surface area is wet by the liquid, call it ##A_{sl}##. The complement of the solid’s area is ‘wet’ by the gas, say ##A_{sg}##. There is also an area of contact...
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### What has a higher total energy?

Homework Statement Why does a satellite that has a 40.0kg mass in its 177km orbit has a total energy larger than its 144 km orbit? Homework Equations Ep = -GMm/r, Et = -GMm/2r The Attempt at a Solution I figured from using the Et equation, the greater the radius the bigger the value, but I...
37. ### Speed, momentum and total energy of a muon (SR)

Homework Statement A muon has a mass of 106MeV/c2. Calculate the speed, momentum and total energy of a 200MeV muon(a muon with a kinetic energy of 200MeV). Homework Equations E=γmc K+mc2=E γ=1/(1-β)1/2 β=(v/c)2 The Attempt at a Solution To solve for the speed I plugged E=γmc into K+mc2=E to...
38. ### Calculate Total Energy: Solve Homework Statement

Homework Statement Homework Equations Total energy = Translational kinetic energy + Rotational kinetic energy Total energy= 1/2 m V2 + 1/2 I W2 The Attempt at a Solution W= v/r = 3.20/0.100 = 32 rad/sec Total energy= 1/2 m V2+ 1/2 I W[2 Total energy = 1/2 (8)(3.20)2 + 1/2 (1.60x10-2)...
39. ### I Determining the total energy released by a compost pile

The heat source for this experiment is a compost pile (1 cubic meter), I know that the inside of the pile will reach approximately 50C for 2 weeks or so. Right now it's winter so the temperature will stay around 0C (average). The thermal conductivity of compost can vary greatly but in this case...
40. ### Finding the equilibrium distance Rsub0 using total energy.

Homework Statement Using the total energy, solve for the equilibrium distance R0 α is given and other constants such as permitivity ε0, avogrado, N, and charge q. Homework Equations Utotal=-Nα(q2/4piε0)(1-ρ/R0) The Attempt at a Solution Tried to plug the values but I can't solve for R0 since...
41. ### Total energy of free electron gas

Hello everyone! I encountered a problem about the specific heat of electronic gas and I do not understand a formula... so the problem says that experimentally it has been shown that the specific heat of the conduction electrons at constant volume in metals depends on...
42. ### I Is the Hamiltonian always the total energy?

I'm working on some classical mechanics and just got a question stated: Is the Hamiltonian for this system conserved? Is it the total energy? In my problem it was indeed the total energy and it was conserved but it got me thinking, isn't the Hamiltonian always the total energy of a system...
43. ### I Quantum numbers - Total Energy and Orbital Momentum

With the quantum numbers l=1, n=2 and m=-1 how do I calculate the total energy E, L2 (the square of the orbital momentum) and Lz (the z-component of the orbital angular momentum. I've been trying for two hours and am getting no were. Please help
44. ### Time period in harmonic oscillation.

Homework Statement Homework Equations Find Time Period. Find the error in my solution. The Attempt at a Solution Where i am wrong ?
45. ### Charge density that minimizes total energy

I am currently interested in a system, where I have a big box of charges for which the density goes to zero at the boundary. What I wanted to do is try to derive what charge density will minimize the total electrostatic energy in the box. Now a cubic box gave me some complicated so I switched...
46. ### How Is Total Energy Calculated for Climbers in a Physics Problem?

Homework Statement Homework Equations ΔU = Uf - Ui ΔW=-ΔU The Attempt at a Solution I am unsure if the question combines both climbers' masses or they each have a mass of 75 kg + the 20 kg they are holding. In a), are they asking for the total work of each climber? Or just the gravitational...
47. ### Capacitance Question - Total Energy, Potential Difference

Homework Statement Two identical parallel-plate capacitors, each with capacitance 10.0 μF, are charged to potential difference 50.0 V and then disconnected from the battery. They are then connected to each other in parallel with plates of like sign connected. Finally, the plate separation in...
48. ### Pathria page 2 -- total energy for mutually interacting particles

In page 2 of Pathria's textbook on 'Statistical Mechanics,' it is mentioned that Consider the total energy ##E## of the system. If the particles comprising the system could be regarded as noninteracting, the total energy ##E## would be equal to the sum of the energies ##\epsilon_i## of the...
49. ### What was the role of Hawking Radiation in the early universe?

Amount of Planck energy is 1.956 * 10^9 J. Was this total energy of universe at plank time at big bang cosmology model? It's clear this amount of energy is not enough for making our solar system, even it's not enough for making mass of me ( 60 kg ). Should we postulate energy increase in the...
50. ### Total energy of the flowing fluid

Homework Statement Since this scanned notes is not clear enough , so I retype some parts of the notes, The enthalphy , h is given by the formula , h = u +Pv = u + P/ ρI want to ask about the total energy of the flowing fluid , which is given by the formula = P/ ρ + e = h + ke +pe = h + (V^2)...