Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [energy]

Energy is the conserved quantity associated to time-translation invariance and represents the work a system is capable of doing. Use this tag for questions about energy, and consider adding [tag:energy-conservation] if it is specifically about its conservation.

1
vote
0answers
22 views

Is there a connection between the energy distribution and time dilation?

Can anyone please help me understand what is descibed bellow? Scenario 1. We have a pair of atomic clocks. Let's call them clock A and clock B. We switch both of them on at the same time. Clock A ...
1
vote
1answer
15 views

Kinetic energy of disk rotating around axis parallel to the one through its center

Given the situation shown in the figure below. A thin disk with mass m and radius r is rigidly connected to one end of a massless rod with length l at its centre, with the other end of the rod ...
0
votes
4answers
34 views

Why does the GPE of an object always equal the work done?

I had a question that said, "If you do 100 J of work to lift an object over your head, what is the gravitational potential energy relative to its starting position? What would be its gravitational ...
-6
votes
1answer
33 views

SuperString theory and mass-energy equivalence [on hold]

I have some doubts regarding Einstein’s mass-energy equivalence relation $E=mc^2$. This equation was also interpreted as release of c2 joule of energy if 1 gram mass of an element is completely ...
0
votes
2answers
41 views

Does potential energy get transferred from my body to a wall when I push a wall and fail to move it?

When I push a rock (and fail to move it), I do not do any work and therefore there should be no energy transfer. But my teacher says that, when one pushes a rock, energy is transferred to the rock ...
2
votes
3answers
151 views

What's the point of momentum?

I know this may sound like a strange question but I have always wondered what exactly the mathematical point of momentum is. I have understood energy to be an attempt to reformulate Newton's 2nd law ...
0
votes
1answer
28 views

Total energy, total momentum of two different balls [on hold]

I have a ball out of plasticine thrown horizontally with speed $v$ on a steel ball that is attached from top to the ground on flexible straps in the middle (see picture). The mass of plasticine is $m$,...
-2
votes
1answer
31 views

How can I calculate the energy or force required to make an object a certain density? [on hold]

I have an object with the mass of 1 gram, the volume of $0.0002192~\rm {cm}^3$ and the density of $4.56 ~\rm g/{cm}^3$ and I need to calculate the force/energy required to make it have a density of $7....
1
vote
2answers
67 views

Electrons Getting mass from energy

According to relation $E=mc^2$ energy and mass are equivalent. So, when an electron in its orbit gets energy from out, does its mass increase? If not, where is the energy stored? I am not ...
0
votes
1answer
25 views

Calculating initial average energy of a thermal state

We are given a system with the Hamiltionian $$H = \sum_i \omega_i a^{\dagger}_ia_i \tag{1}$$ where $a^{\dagger}_i, a_i$ are creation and anihilation operators. I did the calculations and got the ...
-1
votes
1answer
10 views

Can fire create pressure if it released it energy as fast as an explosion [on hold]

Since fire release energy, I wanna know if it can create a shockwave if it release it energy as fast as an explosion
-1
votes
1answer
18 views

Energy recovery from refinery cooling tower

Is there any possibility of recovering exhaust energy from a cooling tower by putting a wind turbine above it? Would this affect the performance of the cooling tower?
0
votes
4answers
84 views

Why do we use heat engines if they are so inefficient?

Let's say I wish to build an engine which will launch a box vertically upwards. I propose two such engine designs: Engine 1 (finger, spring, box) Step 1: Orient uncompressed spring vertically. ...
-2
votes
0answers
29 views

How to calculate $n$? [on hold]

Suppose I want to measure the energy of a light beam of frequency $f$. So I can use Planck's Law $E=nhf$. Then how can I calculate the number of photons $n$? Is there any other formula or way than ...
1
vote
2answers
97 views

Conceptual understanding of Schrödinger equation

So I followed this lecture: https://www.youtube.com/watch?v=qu-jyrwW6hw which starts of with the statement: If you have a Schrödinger equation for an energy eigenstate you have $$-\frac{\hbar}{2m}...
0
votes
0answers
12 views

Magnitude of mass polarization

When solving many-body atomic Hamiltonians, (such as Helium), there exists a term in the Hamiltonian which looks something like: $$ \begin{equation} \frac{1}{M}\vec{\nabla}_i\cdot\vec{\nabla}_i \end{...
-3
votes
0answers
37 views

E greater than V [on hold]

Show that E must exceed the minimum value of V(x) for every normalisable solution to the time-independent Schrödinger equation? This question was given to be proved in David Griffith's ' ...
-7
votes
0answers
44 views

My theory on the Big Bang , energy and the emergence of space. Please tell me what you think [on hold]

The Big Bang did not start with a singularity like a black hole. Entropy only exists when there is something to order. Black holes have an infinitely high entropy. We know that entropy can only ...
6
votes
1answer
193 views

To what extent is the heat in the focal point due to visible light?

When focusing sunlight on a piece of paper, e.g. with magnifying glass, the paper will be charred and might eventually even burn (assuming low cloudiness). To what extent is the heat a result of the ...
0
votes
2answers
51 views

How is a capacitor implemented in Kirchoff's Loop Rule?

I'm real stumped here. I may be missing something, but I'm genuinely perplexed as to how one would add a capacitor to the list of elements being added to an equation through Kirchoff's Loop Rule (KVL)...
1
vote
1answer
89 views

number density of photons and the total energy of the universe

I was reading over some assignment solutions that my lecturer put up and one of them said that instead of calculating the number of photons in the universe with the familiar method of $\int^{\infty}_0(...
0
votes
1answer
49 views

How to analyse the LHC signal for Higgs?

With increasing energy the collision decreases in the plot for signal in LHC. why is that? and at an energy 125GeV the no of events suddenly increases. How this proves that higgs has a mass of 125GeV?
2
votes
3answers
51 views

water pipes break when temperature goes down, how to estimate the energy involved?

Normally low temperature is associated with lower energy state and high temperature with higher energy state. There is an apparent paradox when a water pipe breaks due to low temperature: when ...
-1
votes
1answer
24 views

How does varying power from renewable energy (RE) sources affecting Grid? [closed]

Power from Renewable energy resources vary and fluctuating a lot. This could cause fluctuation on grid's voltage and frequency. Could someone give brief explanation about the process of this problem, ...
-2
votes
0answers
29 views

Calculation of Energy/Power [closed]

Superman throws Hulk up a $150$ meter building by swinging him around achieving the speed necessary. It takes $1.50$ seconds to achieve the speed necessary. What is the energy/power produced by ...
0
votes
1answer
38 views

I am having trouble understanding work and the factor of time

Consider this: 1 kg object vs 1000 kg object No friction applies in my example and the machine I am using is 100% efficient. Some machine using a fuel applies 1 N of force over 1 meter to each object ...
66
votes
13answers
20k views

If visible light has more energy than microwaves, why isn't visible light dangerous?

Light waves are a type of electromagnetic wave and they fall between 400-700 nm long. Microwaves are less energetic but seem to be more dangerous than visible light. Is visible light dangerous at all ...
1
vote
2answers
47 views

In a masses inelastic collision, K energy convert to heat but velocity remain same. we receive heat without losing velocity? how?

I have read the answer about the energy and momentum conservation question but I have a great question now! Imagine we have two masses which one of them is at rest and another move and collide to the ...
0
votes
0answers
27 views

Volcanic Eruption Calculation? [migrated]

So, I was trying to find the amount of energy created during a volcanic explosion, I have been looking around, There was one calculation I saw where I should use the Kinetic Energy which is $E_k=\frac{...
-2
votes
0answers
33 views

Calories and compaction [closed]

If you compacted a 10, 000 calorie meal into a 1 cm cube would it still be those 10, 000 calories?
0
votes
0answers
11 views

Free energy of non-interacting bosons in mean field

The result As a mathematician I am currently struggling to understand Tóth's Phase transition in an interacting Bose system. An application of the theory of Ventsel' and Freidlin. The free energy (...
0
votes
0answers
18 views

Does Oberth Effect work in free space or it works only in gravitational field (gravitational well)?

From Wikipedia article about Oberth Effect it is not clear if it works in free space (no gravity, no air, etc). For example, in very far space between 2 galaxies, gravity is almost zero. There are 2 ...
1
vote
1answer
25 views

Does a field gain energy or does the mass/charge?

My textbook reads that when a mass/ charge is moved into the influence of a gravitational/ electric field the field gains/ loses energy rather than the mass/ charge. How can this be explained?
1
vote
0answers
36 views

What happens to energy when waves cancel out? [duplicate]

So this is basically What happens to the energy when waves perfectly cancel each other? again, but I'm not understanding the answers given (or they don't address what I am confused about) Basically ...
2
votes
1answer
41 views

How do salt crystals evaporate in water?

Salt dissolves in water but when water has evaporated it is still there. What has happened to the salt in the water and why is it still there when water has evaporated?
0
votes
1answer
51 views

Population of conformers in $NVT$ ensemble

I have one question - I've done simulations using Car Parrinello Molecular Dynamics together with Thermodynamic Integration method (liquid phase), hence I have calculated Helmholtz energies for my ...
0
votes
0answers
22 views

Does the energy of two entangled quanta vary with distance?

my question is about,Does the energy of two entangled quanta vary with distance?
0
votes
1answer
47 views

Is There a Limit to The Energy-density Confined to a Black-hole Structure, Consisting of a Schwarzschild Sphere? [closed]

Imagine two particles repeatedly colliding with increasing momentum,like a dense collection of particles confined within the envelope of a collapsing star that's close to becoming a black hole. Is ...
1
vote
1answer
63 views

Energy spacetime warping

If energy warps spacetime, then does light warp spacetime? And if special relativity says that things near the speed of light increase in relativistic mass, then does light have a relativistic mass? ...
1
vote
2answers
47 views

What is the energy of an atomic orbital?

When we refer to energy of an atomic orbital what is this energy ? is potential energy ? but if is potential energy then shouldn't be considered the whole potential energy of the atom ( potential ...
1
vote
1answer
35 views

Irreversible and reversible compression work

Why is work done on the gas when it is compressed from (p2,V2) (pressure,volume) to (p1,V1) against constant pressure external pressure p1 maximum when it is done irreversibly? In reversible process, ...
0
votes
1answer
30 views

Formula for Power from Kinetic Energy

Work Done = $Fd$ Power = $Fv$ If the (net) Work Done = Change in Kinetic Energy, and the object starts from rest: Work Done = $\frac{1}{2} mv^2$ Power = $\frac{1}{2} m av$ Power = $\frac{1}{2} ...
2
votes
3answers
66 views

Photon energy comes in packets

From the HyperPhysics page on the Photoelectric Effect: According to the Planck hypothesis, all electromagnetic radiation is quantized and occurs in finite "bundles" of energy which we call photons....
0
votes
2answers
37 views

Constant gravitational acceleration $g$ and energy

I've been taught the $g$ is constant for different masses and that if I were to drop a heavy object and a light object from the same height then they would reach the ground at the same instant with ...
-3
votes
0answers
39 views

Is angular momentum , energy? [duplicate]

is angular momentum energy? I mean why is the unit of torque N CROSS m and it is not considered energy but the unite of angular momentum is j.s?
0
votes
0answers
46 views

Generic Differential Equation for Oberth Effect

In Wikipedia article about Oberth Effect there is an example of calculation in a simple case when the differential equation is not required. In non-English versions of this article (for example, ...
1
vote
3answers
53 views

How are various forms of energy ability to do work? [closed]

According to various sources that i have come across, energy is the ability to do work. Can someone elaborate how diff forms of energy like potential energy and kinetic energy are ability to do work? ...
1
vote
4answers
85 views

$E=hf$ true for all implies $E=pv$ true for all?

In the answer to this question: Can I apply $E=hf$ to a particle having mass? It was stated that $E=hf$ is true for all particles. If so, doesn't this imply that $E=$momentum x velocity is true for ...
0
votes
1answer
67 views

Work done in accelerating an object in circular motion

In a hammer throw competition, an athlete spins a “hammer” before releasing it. The “hammer” used in this sport is a metal ball of mass 𝑀 = 8 kg and diameter 𝐷 = 30cm, which is attached to a ...
0
votes
1answer
11 views

How to estimate energy of piezo ignighter discharge?

Question for fun. All we know piezo ignighters, these small friends, like following one: They are of quite same size and parameters with rough approximations: same spring, same piezo, same hit force, ...