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.
This is what I have for my solution thus far:
"For gold to transition to mercury, it must exchange one of it's neutrons for a proton via ##\beta##-decay. In order to find the energy of the emitted gamma rays, we must first find the excess rest energy ##Q## present after the ##\beta##-decay. The...
In order to change the radius, additional energy is required, the total energy of mass m on a circular orbit is given by:
$$E_{total} = - \frac {GMm} {2R},$$
The change in energy between orbits ##R## and ##R_{0}## is:
$$\Delta E_{total} = \frac {GMm} {2} \cdot \left( \frac 1 R_{0} - \frac 1 R...
I attempted the problem by first finding the radial, theta, and phi equation for the ground state of a hydrogen atom. I multiplied the three equations to get the wave equation. From there, I took each derivative in the Schrodinger Spherical equation and found that ## \frac {\partial^2 \psi}...
Is it possible to move Stress-Energy tensor to the left side of EFE? R=T => R-T=0. Relativists move cosmological constant Λ to the right side of EFE. Can we move SE tensor to make a vacuum?
I believe that when a photon is refracted it slows. Why is it that the wavelength decreases but that its frequency stays constant?
Does this imply that the photon has not lost any energy in the process of slowing down given that E=hf?
Thanks
I believe that when a photon is refracted it slows. Why is it that the wavelength decreases but that its frequency stays constant?
Does this imply that the photon has not lost any energy in the process of slowing down given that E=hf?
Thanks
I was watching this YouTube video by the channel The Action Lab:
At one point it shows this capillary tube phenomenon:
It got me immediately thinking: Conservation of energy much?
What's stopping that second tube from being bent into draining into the leftmost tube, thus creating an...
Hi, so this is a lab in which we used an air track at an angle and a glider to gather some data through various trials, ultimately to calculate "g". L_glider = 10.15 cm
x (photogate activation point) = 547.5 mm or 54.75 cm
x_0 (release point) = 1800.0 mm or 180.00 cm
(Δx)_midpoint = | x - x_0 |...
I did some algebra and got the final equation mgh=1/2MR^2omega^2+1/2(2/5MR^2)omega^2, then plugged in the numbers and got an omega value of 111.09. Using 1.7 as h instead of cos(17)*1.7=1.63 I got 114.09. Both answers were wrong. Am I missing something, or did I just screw up the math?
From the first equation, there are 5 constants, e, ##\pi##, ##\varepsilon_0##, ##n^2##, and 32. The only difference is m, where helium has around four times the mass of hydrogen. What I don't get is if there is a difference between the energy levels of the hydrogen and the ionized hellium? Also...
If you have 3 observers, one at rest 0c, one at 0.8c, and one that moves between these 2 frames of reference. The observer that moves between the frames starts at 0c and accelerates all the way up to 0.8c. As it accelerates, the observer in the stationary frame sees its momentum, relativistic...
it requires less energy to impart acceleration to an object than to the entirety of the universe, This would break the principle of relativity since the amount of energy to move an object should be the same as the amount of energy to move the rest of the universe. This observation implies a...
I was reading these papers by Sean Carroll (https://arxiv.org/abs/1405.0298; https://arxiv.org/abs/1505.02780) in which, among other things, he argues against vacuum up-tunneling occurring in the universe. He only acknowledged that it would be possible in the first moments of the universe while...
please correct me if im wrong...
at top
highest gpe
ke = 0
elastic energy = 0
upper middle
0=elastic energy
ke < gpe
middle
ke = gpe
lower middle
ke>gpe
bottom
ep = maximum
gpe=ke = 0
rebound
?
part i)
i did 1/2 * 1700 * v^2
i dont know what v is...
so how do i solve it?
part ii)
i calculated it correctly by 440*25
please explain in detail why i used 440?
and part d)
i did 1.7*10^4 = 48000/t
my t= 2.82 s
but correct answer is 3.5s
part d- ii and iii
ii) my answer is
300-140/300 *100
ke at y = 300
and spring energy at max compression is 140
iii) e is directly proportional to x^2
so it increases exponentially
is my explanation correct?
my attempt: i solved it all correct but i dont understand a few things mentioned above...
82.04 * v = 56
so i got v as 0.68 m/s which is correct
but i dont understand the concept...
Writing force equations for block ##m## : $$T-mr\omega^2=m\ddot{r}$$ and for block ##M## : $$Mg-T=M\ddot{r}$$ I think there are mistakes in my equations as they are leading to nowhere and morever i think force methods are really risky in this regard . It would be better to write the total energy...
Does the high temperature increase the kinetic energy of molecules or atoms, or does the high kinetic energy of atoms or molecules increase the temperature ?
I'm so curious about this. Which concept is more accurate between the two
I did: Work done by gravity+work done by applied force= KE(final)- KE(initial)
Work done by gravity should simply be -mgh
=100*5=-500J
For work done by applied force we know:
W=∫F⋅ds
which can also be written as
W=∫Fdscos(θ)
since F is constant i can take that out
W=Fcos(θ)∫ds
here since ive...
In QFT the objects of interest are the n point Correlation functions which contain all the information about the theory and can be used to compute any expectation value in principle. However I cant figure out how to compute the vacuum energy from the correlation functions alone and cant find any...
Imagine an empty void of intergalactic space. In this space there is a cloud of diffuse gas, mostly hydrogen and helium. The gas is non-rotating and very cold just above absolute zero. There is nothing else around this cloud, and so it has a clear center of gravity, and no other objects...
Hello,
I have been reading that a coal power plant and a nuclear power plant have similar efficiencies, i.e. ~30%. This 30% refers to the conversion of thermal energy into electricity. For example, for 100 Joule of thermal energy, we only get 30 Joule out of electrical energy.
How is that...
Hey all. Quick questions for all you NEs and nuclear lovers out there.
I am currently finishing up HS and need to decide a major for college. I am trying to decide between EE and NE, but am strongly considering NE.
I have always loved nuclear energy and anything related to nuclear in general...
So I understand that I have to integrate the negative of the force function to get the change in PE. I get -(20x^2 - 2x^3) and when I evaluate it from 0 to 2, I get -64N. But, of course, the change is positive. What am I missing?
Thank you.
Hello, this question may seem weird but I really need help on this.
To bring the formula for the height h of the triangle above, I have to create a relation between potential and kinetic energies of the black ball with mass m (I can't find any other methods than this).
For a sphere falling...
See also my LinkedIn page under my name, Dirk Smit. I retired recently from a big energy company where I was the corporate chief scientist. I am now affiliated with Oxford Univ and MIT working on the applied science and engineering of the energy transition in particular the role of the...
$$W = W_{gravity} + W_{friction} + W_{air}$$
Dividing by s:
$$F_{total} = mg(sin(\alpha)+\mu cos(\alpha))+0.5×C_{d}A\rho×(v+v_{wind}×sin(\beta))^2$$
Then expressing v for both sections separately:
headwind:
$$0.5×C_{d}A\rho×v^2+v_{wind}×sin(\beta)×C_{d}A\rho×v+mg(sin(\alpha)+\mu...
I think that the second tippe top will spin on its stem first, and the first tippe top will stop spinning first due to its greater mass and lower angular velocity. Here are my ideas:
They are given the same initial energy. By the conservation of energy principle, an object with greater mass...
Thus
$$\Delta K=-\Delta U + W_{nc}$$
$$W_{nc}=\Delta K+\Delta U=\Delta E_m$$
My question is about the following statement
The system is closed. ##\Delta E_{system}## does not necessarily have to be zero. Where does (1) come from?
I am trying to wrap my head around something and would be grateful for some insight. Specifically, why the different electric fields along different paths to different areas of an irregularly shaped conductor don't impart different energies to inflowing particles.
Say we have a negatively...
Hello everyone,
I'm currently working on a physics problem involving the rotation of a 5 kilogram ##M=5## solid sphere subjected to a force of 5 newtons ##F=5##, and I've encountered an inconsistency in my calculations. I'm seeking guidance or insights into where I might have gone wrong.
My...
I've had this question for a while now and I wonder if anyone can make sense of it. It's about two scenarios where the difference between them seems to contradict conservation of energy:
Scenario 1: In a vacuum chamber, there is a robotic arm, a box, a lower platform and a higher platform. At...
Sorry for my questions as an amateur interested in physics: If light changes its frequency during a long time of travel in space (vacuum?) for all observers (redshift) and therefore its energy decreases (E=hf), what "entity" absorbs this energy? I suppose the answer will be that the wavelength...
Start by finding the equilibrium position, so we have {4mgx}/{a} = mg giving us x = a/4, therefore the spring's length is 5a/4. Now the loss in EPE (and therefore gain in energy of the particle) between the bottom and the equilibrium position is clearly 4mg((a/4 + d)^2 , and then from the...
Hi PF, long time no see. Hope you are all well.
Recently I have come into a mental conundrum of a cosmological physical nature.
After doing some napkin calculations about the energy of celestial bodies and transforming them into mass via E=mc^2 I've found that said energy is by no means small...
So first I rewrote H as a matrix:
$$ H =
\begin{pmatrix}
a & b \\
b & c
\end{pmatrix} $$
And tried to find the eigenvalues/energies of H, so I solved
$$ det (H - \lambda I ) =
\begin{vmatrix}
a-\lambda & b \\
b & c-\lambda
\end{vmatrix} = (a-\lambda)(c-\lambda) - b^2 = ac - a\lambda -...
We connect the charged capacitor to the no-charged capacitor (consider the wires to be ideal R=0), the final energy is less than the initial energy of the system. Where is the lost energy? (see example blew)
I believe that this is due to context of application, but now, I'm starting to doubt myself. For example, a helicopter lifting itself has positive PE change. I really don't intuitively understand how this works. Can someone kindly explain this to me?
Hi.
If I drop an inelastic body, its potential energy first gets converted to kinetic, then to deformation energy. We use conservation of energy without taking into account the kinetic energy gain of the earth during the fall.
However, at first sight conservation of momentum seems to be...