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.
1) Considering the forces on one of the moons, I have: ##\frac{GMm}{(10R)^2}+\frac{Gm^2}{(20R)^2}=m\frac{v^2}{10R}\Leftrightarrow v=\sqrt{\frac{G}{10R}(M+\frac{m}{4})}.##
2) Considering the initial situation in which the satellite is at rest on the surface of the planet...
In density functional theory (DFT), electron density is a central quantity. Because of this, we want to calculate electron - nuclei potential energy as functional on electron density. If we know how potential energy varies across space, we can calculate this functional with plugging particular...
Time indepedendent Schrödinger equation for a system (atom or molecule) consisting of N electrons can be written as (with applying Born - Oppenheimer approximation): $$ [(\sum_{i=1}^N - \frac {h^2} {2m} \nabla _i ^2) + \sum_{i=1}^N V(r_i) + \sum_{i < j}^N U(r_i,r_j)] \Psi = E \Psi $$
Terms in...
Here's my list of variables and things to account for:
m=100kg
Wnc=5000J
Wfriction=-500J
-Kinetic energy will be doubled (though I don't know how that plays into it exactly)
-I don't think there's any PE because it's on level ground
My idea of what the equation might be:
Wnc +1/2mv^2initial =...
What is the need to introduce the concept of work and energy when the motion can be completely understood by the concept of force and acceleration and momentum and velocity and displacement, etc?
Why do we need to understand the same thing once again in terms of Work and energy?
Also the kinetic...
Can a system be defined as the transfer of energy between two mediums?
An example of this approach is the Rankine cycle for a power plant (water and steam cycle)
This cycle would be defined by four systems.
System 1 (boiler feed pump)
Energy released by boiler feed pump…...Energy added to...
Hi all,
My question is about Doppler redshifts, but I'm going to mention cosmological redshifts first because I'm a lay person as far as cosmology's concerned (I'm an amateur astronomer and did a few introductory astrophysics/cosmology courses at university, but my degree focus was planetary...
Hello!
I have finished high school quite a few years ago. I did a physics course that went over nuclear fusion and fission, and I quite enjoyed it. However, I unfortunately no longer have those textbooks (I sold them on as many people do). Now I am doing a bit of programming in the field of...
1. From resnik, Halliday “Kinetic energy K is energy associated with the state of motion of an object. The faster the object moves , the greater is the kinetic energy”
If I am right this means that greater the kinetic energy, greater is its speed.
2. Force transfers energy to the body due to...
I am fairly certain that the answer here is to differentiate partially with respect to time rather than fully. In Landau and Lifshitz' proof of energy conservation one of the hypotheses is that the partial of L wrt time is zero. Am I on the right track?
I have read that almost 80 to 90% of our space is made of dark matter or Dark Energy. But what is the function of this Dark matter or energy? Is this something that binds stars, galaxies, etc? If not then what is the actual matter with Dark energy?
Ion traps are very complex, but one of my Physics Olympiad textbooks presents a simplified model of a resonating charged particle in an ion trap
A tuned circuit consists of an inductor and a parallel plate capacitor (capacitance C and plate separation d). It has a resonating frequency ##\nu...
I encountered a problem regarding the appropriate sign needed to be taken for the work done on a dipole when it rotates in a uniform electric field and would appreciate some help.
The torque on a dipole can be defined as
τ=PEsinθ
The work done on a dipole to move it from an angle ##\theta_0##...
Generally, energy is ##U=9\times 10^{9} \times \frac{5\times 10^{-6}30\times 10^{-6}}{2+(10+20)\times 10^{-2}}=0.5869 J##
<br/>
After touching, they have charges
##q_1 and q_2 = 35\mu C-q_1##
##\frac{q_1}{10}=\frac{35\mu C-q_1}{20}##
I was wondering where 1/10 and 1/20 coefficients come...
I'm trying to understand a little bit more about how k-values relate to rate-determining steps and energy diagrams. I always assumed that the lowest value of k (in the forward direction) was the RDS saw something in a handout that indicated otherwise. It explained that even though k1 > k2...
I believe I got the first part of this questions solved.
For part b, we are asked to find the change in internal energy.
We know ΔE=Q+W. The cylinder,gas and piston head are the system. The cylinder and piston head are well insulated, so there will be no head transfer, therefore Q=0.
So now...
While reading about electromagnetism from the OpenStax books with my son (and doing some experiments), he asked this question.
Suppose I hang a pendulum and make it oscillate inside a coil connected to a Galvanometer as shown in the schematic diagram:
Hopefully the image is clear enough. His...
> In the movie "Star Wars: A new Hope", Luke Skywalker blows up the 'death star'. Assume that the 'death star' is a perfectly spherical spaceship with uniform mass distribution. The mass of 'Death Star' ##M=1021 \mathrm{kg}## and the radius ##R=667\mathrm{km}## Estimate the amount of the energy...
a) Two particles have energies E1 and E2, and momenta p1 and p2. Write down an expression for the invariant mass of this two-particle system. Leave your answer in terms of E1 and E2, and p1 and p2.
b) A typical photon (γ) in the Cosmic Microwave Background (CMB) has an energy of kBTCMB, where...
Hello,
I’ll start by saying I have the answers and the steps to the solutions, but there’s a comprehension disconnect somewhere that I’m trying to figure out. There are two parts to my question but the second one may not apply depending on the answer to the first. I wasn’t sure from the forum...
Lets consider T(\vec{p})=\frac{\vec{p}^2}{2m}=\frac{\vec{p}\cdot \vec{p}}{2m}. Then \frac{dT}{dt}=\vec{v}\cdot \vec{F}.
And if we consider
T=\frac{p^2}{2m} than \frac{dT}{dt}=\frac{1}{2m}2p\frac{dp}{dt}
Could I see from that somehow that this is \vec{v}\cdot \vec{F}?
I have doubts about the wording of the exercise:
(1) energy density is ##u=\varepsilon_0 (cB)^2## but since the question asks for mean energy density should I perhaps average over ##cos^2 (\omega t)## (there due to the ##B^2##) and thus use ##<u>=\frac{1}{2}\varepsilon_0 (cB)^2##?
(2) it seems...
When it comes to explaining some phenomena, I think in terms of mechanisms whereas physics explains through mathematics. With this in mind, I'm trying to compare and contrast the differences between the candidate explanations for dark energy, as nicely summarised on the NASA website...
As I understand, the main theoretical virtue of Guth's inflation hypothesis is that it explains a bunch of otherwise hard-to-account-for phenomena under the standard big bang model without inflation: the Horizon Problem, the Flatness problem, the Monopole problem, and also the problem of how...
With the latest view that free space has virtual particles constantly popping in and out of existence, is it now rational to argue that light can electromagnetically travel through free space for ever and ever without the slightest energy loss? Edwin Hubble found that the general red shift of...
Hi all, I'm not a physics student (although I have a PhD in a different field) and so don't have the math, but I'm trying to interpret a key passage from Krauss' book 'A Universe from Nothing' where he is (trying?) to explain, in 'layman's terms', what Alan Guth termed 'the ultimate free lunch'...
Iron (Fe-56) is in terms of nuclear energy spent, which seems equivalent to saying its nuclides are the most tightly-bound. Does this also make Fe-56 the most stable nucleus, and is nuclear potential energy to stability a general correlation? Do more-stable nuclei generally have less nuclear...
The classical definition to the Kinetic Energy equation is KE=integral of F*dx where F=d(m*v)/dt. When mass is constant, KE=(1/2)m*v^2.
I am working on a vibration problem at work and having to review my Lagrangian Dynamics books from 30 years ago. So my question is about all of the authors...
I have used the work energy theorem like all source have shown me an have arrived at the right answer
where work one by all the forces is the change in kinetic energy
-1/2kx^2 - umgcosΘx +mgsinΘx = 0 is the equation
which becomes
-1/2kx -umgcosΘ+ mgsinΘ = 0
where k= spring constant
u=...
I tried to find states in direct method using ##\frac{E}{E_0}=\:nx^2+ny^2+nz^2## and ##100\:<nx^2+ny^2+nz^2\:<\:136##
But it was too long, found it using phi approximation there are around 300 energy states, and Python find around 271 states using direct method but I need manual or recursive...
When the pendulum is released, the Kinetic Energy should be 0. When the pendulum is at the bottom/hits the rod, it should have 0 potential energy. However, I don't quite understand what happens after it hits the rod.
During equal thickness interference, adjust the inclination of the two plates to expand the spacing of interference fringes to 10mm.
Then, if a light with a width of 5mm is used for equal thickness interference, whether an interference pattern will be observed, and the width of the interference...
In the initial position the spring is previously compressed, then the block adds a force, and the spring is again deformed. I think the energy balance is incorrect; the potential energy of the spring is repeated.
Hi all,
I am currently trying to prove formula 21 from the attached paper.
My work is as follows:
If anyone can point out where I went wrong I would greatly appreciate it! Thanks.
Been 20 years since college physics. I have a problem where there are basically two inertia wheels on separate shafts coupled by a clutch. One wheel is spinning and the other is at rest. The clutch engages and connects the shafts. What's the final rpm of both wheels? I'm struggling to find a...
Hello!
I had a random question while playing around with a garbage can that I hoped y'all could help me walk through:
Let's say that I have a hinge on a table, rotating with gravity acting perpendicular to it. Energy is provided into the hinge, let's say by a spring, like so:
I want to know the...
My attempt:
Let ##M_e## be the mass of the Earth and ##M_m## be the mass of the person. Let ##D_{EM}## be the distance from Earth to Mars and let ##R_e## be the radius of the earth.
Defining these constants (leaving off units for brevity):
Masses in Kilograms (G is not a mass but I'll leave...
u = (9*10^9)(1.61*10^-19)^2 * (1/[3*10^-15 ]- 1/[2*10^-10])
u = 7.68*10^-14 J
but here the question. I have been taught that W= -U so shouldn't the answer be negative??
When i look up at the solution all other sources say that the W = U and therefore the answer is in postive.
Burning waste in a waste-to-energy plat, can more energy be produced by burning the trash then the amount of energy needed to heat the trash to the point it vaporises? (to turn it to ash)
eg we have 100 J of energy inside some rubbish, and this energy would all be released when we incinerate the...
Hello! If I have a single ion traveling at a given energy (on the order of 10 keV), is there a way to read out its energy in real time with a single pass? Basically I was wondering if there is a device able to measure the current or magnetic field induced by the ion passing through it (while...
I have two questions:
1) Is it possible to cut the material with a laser cutter or scissors or do I need to have a specific tool?
2) What is the best way to attach the PZT-5H material to the beam but it can be easily detached for using it on another beam ( so no epoxy glue)?Thank you
I was enjoying my (very short) hot shower this morning and realized that the lovely warm water was flowing over my body (sorry - too much information) only once and then disappearing down the drain.
This water - and what comes out of the washing machine, dishwasher etc. could be at a seriously...
Energy and mass are interdependent and electrons can manifest as particles and fields as do all other particles, but is it generally true that physical(classical) matter is a peculiar type of energy that can(for some reason? What?) manifest as physical objects?
Hello, in one of tasks of my liquid scintillation lab is to determine the average energy. You can see from the graph that data I obtained is similar to this one that I have a excel sheet data.
X-axis is for beta particle energy from 0-156keV while y-axis counts of the particles.
So according to...
Why the wheel moves? I intuitively think that it should move to right but I don't really understand why. When AB gets longer by x each end gets longer by x/2 so W goes to right and down. This will create torque and body will move. This explanation seems valid but I can't calculate anything and...