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Questions tagged [mass-energy]

The special-relativistic relation connecting energy with mass, $ E^2 - (m c^2)^2= (pc)^2 $. May be used to provide accounting constraints in energy and momentum, both conserved in total, even in reactions where $m$ is not.

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1answer
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Does Electrostatic potential energy bend Space-time? [duplicate]

Okay, there are various questions. First, "matter and energy bends space-time" does this mean any form of energy can bend space-time? Does theory of relativity assume that there is no other form of ...
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Is the slowing of time with speed exactly proportional to the increase of mass with speed?

This article on time dilation explains how time slows and mass increases with speed. Are they proportional? And is time dilation with a specific speed-mass equal to the time dilation with a ...
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What's the most likely mass for ethanol?

I am interested in learning a little about mass defect and calculating the molar mass of ethyl alcohol. I found this table of atomic weights and would like to use it to compute the mass of the ...
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What is the reason that conservation of momentum is conserved in nuclear reactions?

I understand that in nuclear reactions such as fusion or fission, it is known that energy released due to the mass defect to obey the conservation of energy. However, researching online; I fount ...
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Relativistic energy density (dust, presureless gas or number of particles)

The basic question on the relativistic energy density of the dust (pressureless gas or some number of moving particles). I assume that for some group of particles it is intuitively obvious to write ...
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Matter-antimatter reactions

It's widely known that, using famous equation $E=mc^2$, we can estimate energy in nuclear reactions, matter-antimatter reactions (the most powerful in the universe), etc. It's also known that, in the ...
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What does it mean to SQUARE the speed of light? [closed]

$E=mc^2$ But what exactly does it MEAN to square the speed of light? Like, what is happening in the universe at that point in the equation?
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$H_2O$ vs $2H^+ +O^{2-}$

I am wondering the mass deficit between 2*H + O and H2O. I.e. if I would know the accurate mass of one atom of hydrogen on it's own and the mass of one atom of oxygen on it's own how much of a ...
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2answers
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Mass reduction due to emission of photons

when a torchlight emits a photon of energy E, will its mass reduce by (E/C^2) according to mass energy equivalance? if no what will be the reduced mass?
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Does $E=mc^2$ apply to electron shells with different energies? [duplicate]

Is this statement true: Each electron shell has a different energy level, with those shells closest to the nucleus being lower in energy than those farther from the nucleus. Mass of electron $= 9....
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Is the GW170817 event evidence or counter evidence for Dark Energy?

I've always figured there must be a simpler explanation for the observed extra red shifting that has lead astronomers to hypothesize Dark Energy. Or at least there must be a simpler explanation of ...
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Time dilation, mass-energy equivalence, and implications for the passage of time [closed]

I'm an amateur physics enthusiast, and there is a question that's been in the back of my mind for some time that I haven't been able to answer on my own. First, I want to define a couple of terms and ...
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Mass and energy of radiation

We know that mass can be  converted to energy and vice versa. So does the mass of molecules or atoms change when they absorb a radiation and go to the higher energy state?
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What is the proof for the relativistic expression for kinetic energy?

In his book on relativity, Albert Einstein states in chapter 15 that we now don't write kinetic energy as $K_e = \frac{1}{2}mv^2$ but as $$K_e = \frac{mc^2}{\sqrt{1- v^2/c^2}}-mc^2.$$ How is this ...
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What really causes radioactivity?

We know that a nucleus can transform itself by many ways such as fission, alpha decay, beta decay, etc. But what is it that propels this to happen? Is it just the instability of the nucleus in general?...
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How does positron emission happen naturally? [duplicate]

How does positron-emission happen naturally, for example in Potassium-40? Isn't the added mass of the neutron and the position more than the mass of a proton? Where does the proton get this extra ...
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2answers
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Does light have mass? Why? [duplicate]

I've been wondering whether light has mass. Yet given the wave-particle duality of light, the statement seems to be affirmative. With that, how to calculate it?
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How could 'rest mass' and 'invariant mass' be the same?

The terms rest mass and invariant mass are often interchanged, however i cannot reconcile these concepts: Consider a photon ...
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1answer
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$E = mc^2$ derivation thought experiment seems to not have conserved energy

There is an interesting derivation of $E=mc^2$ given here which I have updated to use relativistic momentum and relativistic kinetic energy. I find when doing the derivation that it doesn't appear ...
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3answers
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On existence of mass in different form [closed]

(I'm a mathematician actually. This is my first question on this site. So please go easy on me if it's a trivial matter or mistake) Lately I've been thinking about special relativity. The thought ...
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1answer
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Is the equivalence of mass and energy a direct consequence of SR or not?

Special relativity gives us the invariance of four-vectors. Consistency with Newtonian physics implies the conservation of four-momentum. The spatial part of four-momentum is $P^0=m\gamma(v)$ ...
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1answer
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Do wormholes have mass that depends on the spacial separation, the temporal separation, the relative motion of the two ends of the wormhole [duplicate]

If there was a wormhole connecting two spatially/temporally separate locations, would it have mass that depends on the spacial separation, the temporal separation, the relative motion of the two ends ...
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Is the ADM Mass for a boosted black hole $M$ or $\gamma M$?

If you were to take the metric for a Schwarzschild black hole and "boost" it, such that it were traveling with velocity $v$, would the ADM mass, corresponding to a time translation, be $M$ or $\gamma ...
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Conservation of linear momentum with mass defect

Suppose we have an insulating container, like a perfect black body, which absorbs all the radiation coming from a radioactive element placed in the center (or some equivalent process like matter ...
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1answer
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Can dark matter actually be gravitational radiation?

It seems to exist like only space distortion, and it seems to move just like radiation (specially when galaxy clusters collide, dark matter goes trough unaffected just like some type of radiation). ...
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Why do electrons have rest energy?

E=mc² so inserting the value of m and c we get 0.511 MeV for electron but then what does this energy account for coz according to me electrons are not made up of any particles so this doesn't account ...
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Does the electric field of a charged particle really contribute to its mass? [duplicate]

An electron at rest creates a static distribution of an electric field around it. Wherever the particle moves, it carries or drags the field with itself. Does this electric field contribute to the ...
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What is the mass of photon? [duplicate]

I'm sorry if this question is asked before, but I searched through the site and none satisfied me. In most of the books I've come across, they just write "rest mass of photon is zero." But never talk ...
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Is there any known experimental violation of Einstein's $E=mc^2$?

Note that I am not talking about $E_0= m_0c^2$ but $E=mc^2$, where m is the relativistic mass. I know that one holds for stationary particles, moving particles, even light, I read that it even holds ...
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Released energy in a reaction

I'm having some trouble in understanding how the released energy in a nuclear reaction is actually calculated. I think I understand the general approach if we are dealing with a reaction like $$\rm ^{...
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2answers
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Why does a particle, e.g. a proton, at rest have $v=0$?

Given the formula $E=mc^2$, the mass is equivalent to energy through the speed of light. This equation is also the special case of $E^2=(mc^2)^2+(pc)^2$ when $p=0$. Thus, it is at rest respectively ...
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Calculating binding energy from mass defect

I am trying to wrap my head around the relationship between binding energy and mass defect. I have read that the difference between the binding energies of the products and reactants of a nuclear ...
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2answers
192 views

Why is the equation $E=mc^2$?

The equation $E=mc^2$ never made any sense to me. c is a constant (speed of light), therefore c squared is also a constant. We're not specifying any units so surely the equation should be reduced to ...
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1answer
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How to express the $Q$-value for alpha decay in terms of binding energy of the relevant species?

I have 2 questions regarding the solution to the following question: The solution states that: Mathematically, I understand how the end result $$Q=BE\left({}^{A-4}_{Z-2}\mathrm{Y}\right)+...
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1answer
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Do Quarks decay into Photons at high enough temperatures?

At high enough energy, particles lose coherence and are ripped apart into a Quark-gluon plasma where the individual quarks can break free of the atomic nucleus and fly around unencumbered. A black ...
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3answers
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Why Didn't the Energy-Momentum Relation Work?

I am currently studying for the GRE Physics subject test by working through published past tests. My question is about problem 20 from the test GR8677: A positive kaon ($K^{{}+{}}$) has a rest ...
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1answer
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Lavoisier law of mass conservation vs. conservation of energy

Lavoisier law states that for any isolated system, mass must be conserved over time. Also, Einstein's equation $E = mc²$ shows energy-mass equivalency. So, since mass must be conserved and energy ...
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In special relativity is mass just a measure of all other energy than kinetic?

The energy momentum equation in special relativity is: $$E^2=(pc)^2+(mc^2)^2.$$ and it holds for a moving but not accelerating object. One special case is the massless photon: $$E=pc.$$ And another ...
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How to understand $E=mc^2$?

I am trying to understand Einstein's mass-energy equation $E=mc^2$. Knowing about the atomic bomb I am inclined to believe that $E$ is proportional to the mass: $E=Cm$. For this equation to be ...
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Question about $E=mc^2$

When a nuclear reaction happens, the amount of mass disappeared satisfies $E=mc^2$. However, the reaction will stop at a certain point, there is no way to make the whole thing disappear into energy. ...
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4answers
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Is there a limit to the amount of mass we can concentrate in a region of space?

Black holes are solutions to Einstein's Field Equations. Black holes contain a singularity hidden from the outer universe. As I understand, these singularities are infinitesimal and contain a very ...
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Is fission/fusion to iron the most efficient way to convert mass to energy?

Is fission/fusion of any element to iron-56 (or nickel-62?) the best way to convert mass to energy, that doesn't involve black holes? In other words, will we be always limited to convert only about 1%...
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1answer
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Effects of Relativistic/Inertial Mass

What would happen to a ball of ice in a remote region of space if spun in a circle accelerating toward the speed of light? As the ball of ice approaches the speed of light, does it melt/sublimate as ...
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3answers
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A spacecraft orbiting the sun charges a battery which becomes a tiny bit more massive. How does this effect the velocity of the spacecraft?

According to $E=mc²$ the spacecraft which stores the Energy from the sun becomes a tiny bit more massive. how does this effect the impulse of this spacecraft. Would it grow because P = (m + extra mass)...
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What is the relativistic energy of a bounded static particle?

Premise: The speed of light is set $c = 1$. Let's consider an electron in an external electromagnetic field. Its four-momentum will be $$p^{\mu} = (E, \bar p) = (\gamma m_e, \gamma m_e \bar v),$$ ...
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Is there a known mechanism for mass-energy distorting spacetime?

I’ve been really interested in learning about the mechanisms behind physical phenomena that go beyond just learning to manipulate the equations and give a physical intuition about HOW something ...
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Does a black hole singularity compress mass back into energy? [duplicate]

I was watching this PBS spacetime video which made the case that mass is just a form of bound energy. Essentially massless particles are confined in a small space giving particles the illusion of mass....
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Is spacetime volume preserved in presence of a mass in General Theory of Relativity (GTR)?

In many publications about the warping of spacetime in presence of a mass the metric of spacetime is stretched, expanded : http://discovermagazine.com/~/media/Images/Issues/2015/april/relativity.jpg ...
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Do photons bend spacetime or not?

I have read this question: Electromagnetic gravity where Safesphere says in a comment: Actually, photons themselves don't bend spacetime. Intuitively, this is because photons can't emit ...
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1answer
38 views

Binding energy and strong force

If binding energy is responsible for holding nucleons together than what is meaning of strong force?