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.
Homework Statement
Question 8 how do we solve it?
Homework EquationsThe Attempt at a Solution
I thought it was B but i don't have a key or any guide. This book was used and the answer written by the previous book user was C. Why?
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...
I am trying to show that
$$
\frac{\Delta v}{v_{c_1}} = \frac{1}{\sqrt{R}} - \frac{\sqrt{2}(1 - R)}{\sqrt{R(1+R)}} - 1
$$
where ##R=r_2/r_1##.
##r_1## is the radius of the circular orbit 1 and ##r_2## is the radius of the circular orbit 2. Similarly, ##v_{c_1}## is the velcotiy of the circular...
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
1. Consider the boron oxide molecule, BO, in the ground state.
(a) Calculate total energies separately for each of B and O atoms (in their ground states).
Homework Equations
(1 Hartree = 27.212 eV, 1 eV = 23.045 kcal/mol).
The Attempt at a Solution
Etot =...
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...
Homework Statement
"Consider a perfectly homogeneous and isotropic universe filled with dust of uniform density ρ(t).
Let universe expand, dust is carried radially outward from origin.
Conservation of total energy E. E = K(t) + U(t)
K(t) = (1/2)*mv^2(t) and U(t) = -GMm/r(t)
where M =...
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
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