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.
If we have a photon being converted to a positron-electron pair, but we lack enough energy for this to happen (hv<2Me*c^2) but the difference is smaller than the uncertainty amount, such that tunneling may be possible, would the resultant pair have net negative energy? Would tunneling even be...
Summary:: I have an assignment that is looking at how a bicycle pump is used to push air through a turbine to generate energy. I need to determine the energy input and energy created. I'm hoping I can get some direction on where to start.
The concept is straightforward. A bicycle pump of...
Summary:: this is what I've done so far... i don't think it works since i believe the information given is not even enough.
the formula I've used are
1. relativistic total energy = rest mass energy + kinetic energy (line 1, 3)
2. conservation of energy (line 4, 7, 8, 9)
3. conservation of...
I was just think how we could calc the power that we need to do {obviously, in general/average, since varies from person to person} to hold an object
But we know the force we need to apply is equal mg.
I am pretty sure that this question is very comprehensive and because of this it becomes...
Vf = ?
y = ?
ME = mgy + 1/2mv^2
ME = 56*9.81*y + 1/2*56*1^2
Ui + Ki = Ui + Ki
gyi + 1/2vi^2 = gyf + 1/2 vf^2gyf = 1/2vf^2
vf = 5.425 m/s
9.81y + 1/2*1^2 = 9.81*1.5 + 1/2*5.425^2
y = 2.949 m
MEi = 56*9.81*2.949 + 1/2*56*1^2
MEi = 1648 J
The picture for this problem really confuses me. I am...
Hi all,
I've read so many times that "temperature is a measure of the average kinetic energy of the molecules in a substance," or sometimes "particles" to encompass atoms and ions too. But how big can "molecules/particles" be before their kinetic energy is no longer relevant to temperature?
If...
This is section 16.3 of QFT for the Gifted Amateur. I understand the concept of the spacetime propagator ##G^+(x, t, x', t')##, but the following propagator is introduced without any explanation I can see:
$$G^+(x, y, E) = \sum_n \frac{i\phi_n(x)\phi_n^*(y)}{E - E_n}$$
It would be good to have...
Hello, I request inputs about selecting a journal to submit an article in High Energy Physics. This is in formal theory as opposed to Particle Phenomenology. The article is more than ten pages so PRL is not an option. How would you choose between JHEP and Physical Review D? Which is rated higher...
I am not sure I understand the question. I imagine there is a horizontal table and all the diagrams are the top-view of the table.
The question states that "A particle moves from P1 to P2 without acceleration along five different paths". In the first picture, I think the path is in the shape of...
Not sure how the problem set up initially as no diagram was provided in the question. Please help me to start with the solution. Your assumptions and educated guess are appreciated.
If this question asked for internal energy, then it is a straightforward thing, just use the formula U = (3/2) nRT = (3/2) PV. But the question specifically asked for average translational kinetic energy which I'm stuck with the value of T to plug in into the formula as the question only give us...
IS my solution right? Comparing with the other solutions, the answer just exchange the signals, i don't know why,
THats what ifound.
And here is the three equations:
{i use the point which occurs the collision}
Lo = Lf >>
0 = Iw + M*Vcm(block)
Eg = ct>
mvo² = mvf² + MVcm² + Iw²
I = ml²/3...
Hey everyone,
I've got a question on converting bound protons into neutrons.
a. What are some methods used to achieve the proton-to-neutron conversion in atomic nuclei?
I'm familiar with particle scattering off a proton in the nucleus. I'm also aware of (n,p) reactions. Are there any other...
Hello!
I was wondering if it is possible to express the gravitational energy as a product of the gravitational field by a moment, as we do with the magnetic and electric energy? Would this require the existence of bodies with negative mass? How could we relate this to the existence or total...
Hi,
I have a question regarding Phonons and daily experience:
Let's say I have a table and I hit it, does it mean Phonons were created where I've hit on the table?
Meaning: By hitting the table, I'm giving energy to it, this energy goes to the motion of the table atoms, and this motion of the...
I use an example with a rack and a pinion. I suppose there is no losses from friction. I suppose the masses very low to simplify the study, and there is no acceleration. I suppose the tooth of the pinion and the rack perfect, I mean there is no gap. There is always the contact between the rack...
Starting from the center of mass energy S = (E_{1} + E_{2})^2 - (\vec{p_1}+\vec{p_2})
knowing that E^2 = m_{0}c^4 + p^2*c^2 one has
S = (E_{1} + E_{2})^2 - (\vec{p_1}+\vec{p_2}) = ( m_{0}c^4 + p_{1}^2*c^2) + m_{0}c^4 + p_{2}^2*c^2)^2 - p_{1}^2 - p_{2}^2 - 2p_{1}p_{2}cos \{theta}
and then...
Hi,
I read the Feynman's book about the quantum electrodynamics and I realized, that he was talking about the different speed of photons. I know, that the light travel's "slower" in a material, but he is also talking about the different speed of photons. I read on the web, that some photons...
I've marked the right answers.
They mainly indicate at power carried by the particles being zero, and here is my doubt- why should it be zero? Shouldn't it have some definite value?
I do understand that the kinetic energy is max at the y=0 and potential energy is max at y=A, but I don't know...
1. The student should use a rubber band, g-clamp, a retort stand, boss and clamp, a mass hanger, 100g masses and a metre rule.
The rubber band should be positioned to hang freely from the retort stand, held in place by a g-clamp to the laboratory bench. Measure the length of the rubber band...
Recently, I have been studying some solid-state physics and I came across this ##E-k## diagram online. Here's an image for reference to what I am referring to...
When does an object have rotational energy? Is it only if it rotates around an axis within the object? Does for example a ball attached to a string with a uniform circular movement have rotational kinetic energy?
I quite understand the fact the EPE (Electrical Potential Energy) of a system of two charges are U = k*qQ/r, Q is fix. however when it comes to three charges i get lost. because my reasoning is :
if q1 is fix then the EPE of the system when q2 is brought is U2 = k*q1*q2/r12, when q3 is brought...
So let's assume ideal wire, resistance = 0 Ohms. Also assume there is a magnetic ball 1 meter away and is attracted to the solenoid.
If you have a loop of wire and run a small current through it, you get a magnetic field. This field attracts the magnetic ball, over a distance of 1 meter.
If...
Definition of conservative field I use:-it is a field in which potential energy of system is independent of path taken.
I understand that it is independent because whenever we take some path than all the perpendicular displacements with respect to force are not counted and if we go further than...
The energy spectrum of a particle in 1D box is known to be
##E_n = \frac{h^2 n^2}{8mL^2}##,
with ##L## the width of the potential well. In 3D, the ground state energy of both cubic and spherical boxes is also proportional to the reciprocal square of the side length or diameter.
Does this...
I'm trying to make up an example for my students to illustrate that in nuclear decay, mass-energy and momentum are both conserved.
I found this problem: https://physics.stackexchange.com/questions/304277/calculate-velocity-of-radon-220-nuclear-after-decay
I am trying to modify it so that they...
It will try to produce a neutral atom but it depends on the amount of energy that electron is shot at the atom, if it is great enough energy for ionization it will produce cation, If it is not enough for ionization it will make a neutral atom or anion, I think.
I have an ordinary switchable magnet for holding tools to a lathe. It's like a magnetic force gearbox, but I can't quite understand the force multiplication.
When placed on a steel surface the switch force is approximately ~5N on both finger and thumb at 1.5cm radius acting over a 3cm arc...
as far as i understand nuclear fission is the splitting of a heavy nucleus cause of a added neutron
the energy you get is cause of the lost mass from binding energy.
but i also read that the nuclear fission products undergo beta decay which emits beta particles gamma rays and antineutrinos
so...
How did you find PF?: We can derive the equation 1/2mV2. But what is the fundamental reason behind mV2(total energy) is divided by half?
I find only derivative solutions to this question. But still unsatisfied.
Spring has more potential energy when it is compressed or stretched from its initially balanced state. As external work is done, it stores energy in the form of potential energy. Here, we know energy is stored in spring but For the Earth-ball system, where the energy stored?
Hi
I've attached the image of the circuit. My first thought before connecting it: if I connect it, I must consider the fact that current cannot circulate suddenly, because a sudden change in the amount of current should imply an infinite value in \dfrac{\Delta{I}}{\Delta{t}}, and a infinite...
Models like Vilenkin's tunnelling from nothing model described here:
https://www.sciencedirect.com/science/article/abs/pii/0370269382908668
claim the universe came from "nothing". It is claimed this doesn't violate any conservation laws because the negative energy of gravity and the positive...
For a system of two or more particles, it is customary to define potential energy functions ##V_{ij}## between pairs of particles, so that the total conservative force (not necessarily total) on any given particle is $$\mathbf{F}_i = \sum_{j\neq i} -\nabla_i V_{ij}$$as a sum over all other...
"The force is zero" means the total force act on the particle is zero? Then there must be an external force. If not, then Fx=0 ?
since Fx = d(U(x))/dx, the answer of (b) should be (i), but how about (a)?
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...
The canonical ( Boltzmann) distribution law for a canonical system is described the probability of state ##v## by ##P_v = Q^{-1} e^{-\beta E_v} ## where ##Q^{-1}## is the normalization constant of ##\sum_v P_v = 1## and therefore ##Q = \sum_{v}e^{-\beta E_v}##. Chandler then derives ##...
Hi!
Situation: quasi-free electron in a 2D lattice, considering atomic potential V(r) = exp{-|r|/b} (r is the distance from the atom)
I'm trying to compute the first five energy gaps at point (10),
firstly I don't understand the meaning of calculated 5 energy gaps at one point and usually we...
This isn't right, is it?
-\dfrac{GM}{R}+\dfrac12 v^2=-\dfrac{GM}{R+h}
v=\sqrt{\dfrac{GM}{R}}\left( 1-\sqrt{\dfrac{R}{R+h}}\right)
He's doing energy conservation. The mechanical energy at the Earth's surface is equal to the energy when the speed is 0.