Tagged Questions

The special-relativistic relation connecting energy with (rest) 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. Use for all manifestations or consequences of the relation.

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As electron is accelerated nearly to the speed of light what would occur? [closed]

What would occur if an electron at rest was accelerated nearly to the speed of light? Would the photons emitted by the electron approach a gamma wave photon as it approached the speed of light, or ...
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Can we work out how fast we are traveling by looking at our mass?

If we (the galaxy) were traveling close to the speed of light; relativity says we would need proportionally more energy to go faster. Given that relative to the cosmic microwave background, the Local ...
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Is there energy output when mass moves between two spacetimes [closed]

Is there energy output when mass $m$ moves between two spacetimes? Say, it starts in a flat spacetime and then falls into a black hole (other examples don't come to mind, but this doesn't mean they ...
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What is the mass and density distribution of a Schwarzchild black hole in the viewpoint of distant observer?

According to Schwarzschild metric the density element $$\frac{\mathrm dm}{\mathrm dV}$$ becomes infinite on the event horizon if there is mass $$\mathrm dm > 0$$very near at the outside of ...
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Why does matter/antimatter only produce gamma rays?

According to wikipedia, all antimatter annihilation produces gamma rays (along with potentially other elements). Why specifically Gamma rays? Why not electromagnetic waves of other wavelength?
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Black Hole: mass density or energy density? [closed]

Recently, I read a quora post in which the OP asked the following question: Can a black hole be formed from accelerating a body and increasing its relativistic mass to the level of a Schwarzschild ...
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Source of energy for infinite expansion

I read in several sources that matter, dark matter & dark energy contributes 5%, 26% and 69% of the known universe. Also, I read in a slide deck about Big Bang theory on nobelprize.org that total ...
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Weight loss of a flashlight due to light emission

I watched this video. At one point, the man explains how a flashlight loses some mass due to light emission when turned on. OK, I get that. Then he talks about a different situation, where the ...
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Why Do Glueballs Have Mass, When Individual Gluons Are Massless?

From Wikipedia Glueballs Glueballs are predicted by quantum chromodynamics to be massive, notwithstanding the fact that gluons themselves have zero rest mass in the Standard Model. Glueballs with ...
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How did physicists conclude that 98% of mass is due to the strong force?

On a video on YouTube called 'weak and strong nuclear force (9/15)' at 0:55 a scientist said that 98% of mass is due to the strong force.
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Why can't a nucleus become a black hole?

A nucleus is very small and very dense. Its density is approximately $2.3 \times 10^{17}~\mathrm{kg/m^3}.$ So why can't a nucleus itself become a black hole?
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what mph of wind would it take [closed]

a 3 foot 2x4 on a 10 degree slant end to end laying on a hard surface. The 2x4 weight is 3.63 pounds . What mile per hour of wind would it take to move the 2x4 completely off the surface. Lets also ...
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Black Hole mass

Where is the material that has past the event horizon of a black hole stored/kept? Does it become pure energy once it passes the event horizon? Does the singularity at the center of the black hole ...
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Does a planet/star itself lose mass when it 'emits' gravitational waves?

Orbiting planets and stars can create gravitational waves, as seen with the LIGO. But are they also losing mass-energy. Beside that, the kinetic energy associated with their orbital angular momentum ...
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Fast moving black hole with low rest mass [duplicate]

Sorry for probably very stupid questions but.. If the massive body with small mass (one of the twins, for example) accelerates until the speed close to the speed of light, the mass of this body as ...
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Why does c^2 appear in E=mc^2? [closed]

I always wondered what relevance the speed of light has in a formula that describes the relationship between energy and mass. I always think of c as a line/vector, and c^2 as a plane, but that does ...
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Is critical mass of fissile material the same in gravitational fields with different force?

Let's take plutonium-239 for example. $10\, Kg$ (sphere $9.9\, cm$) need for a nuclear reaction. Are we talking about these numbers in Earth environment with $\approx 9.8\, m/s^2$ gravitational ...
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Creating matter from energy

I know this is simplistic but can we surmise that is it theoretically possible to reverse the process of a burnt out matchstick (with a lot more energy) and recreate "the match stick matter"? Sorry,...
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Is mass relative? [duplicate]

This question has to do with the relativistic mass of an object. I have been reading that as energy increases, so does mass to a much lesser extent, and that this applies to kinetic energy as well. ...
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Gravitational force between Earth and Sun is decreasing

According to one of the most famous equations in physics, i.e. $E=mc^2$, the mass of the Sun is decreasing as it emits energy. So there must be some kind of disturbance in planetary orbits, and if ...
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Can light change the shape of a black hole?

If light orbits a black hole without ever getting closer or further from it, and the black hole pulls on the light from all directions nearly simultaneously, does the black hole extend at its equator? ...
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Why isn't mass still being created in the universe? [closed]

I was watching a lecture by Alan Guth and wished I was in the classroom to be able to ask a question. He explained that the total energy in the universe could be very close to zero since mass and ...
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Is a puffy object heavier than a contracted object?

From here, I know the spring becomes heavier when potential energy stores in it , how about gravitional potential energy? Is the case similar?consider a puffy object, eg, a gas giant, when it ...
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If matter cannot be destroyed, does that mean that these particles are created somewhere else after breakdown but in the particles original shape?

In the electron collider, after the breakdown into smaller particles, these particles last for a fraction of a second, and then they disappear. My question is: If matter cannot be destroyed, does ...
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Could I make a machine that runs on dirt?

This may sound really stupid, but all matter can be converted into energy. So couldn't it be possible to build like an engine that you'd fill up with dirt and it would run. I understand they're would ...
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Difference between KE “relativistic” mass and heat mass

I have been told in several answers that the term "relativistic mass" is no longer considered adequate wrt. the mass/energy increase in KE. Yet, I read that 1 Kg of gold's mass ingreases by 10^-14 Kg ...
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Does $E=mc^2$ mean that an object with mass $m$ travels at the speed of light in empty space? [closed]

I cannot wrap my head around this (Im new to physics), and this concept is troubling me. I think no, but im not sure why?
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Is an extended spring gain mass from potential energy? [duplicate]

Is it true that when a spring is extended, potential energy is stored in spring and result in gain of mass of the spring?
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Does a gluon have mass or not?

I was under the impression that gluons had no mass. Then Wikipedia throws this curveball: Mass: 0 (theoretical value) < 0.0002 eV/c2 (experimental limit) Which one should a poor ...
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Which one of these energy formulas is correct? [closed]

Which one of the following formulas is correct? What do they mean/represent? How are they used? $E=mc^2$ $E^2=m^2c^4+p^2c^2$ $E=\frac{mc^2}{\sqrt{1-\frac{v^2}{c^2}}}$
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Why can´t we call the energy released after the annihilation of a particle and its antiparticle pure energy? [closed]

As a particle and its antiparticle annihilate each other a huge amount of energy is released, and no mass is left. This energy always comes in the form of force mediating particles (photons, gluons). ...
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Composition of energy of electron? [closed]

Mass energy of electron is 0.510 998 9461MeV/ c2 1) Does it include energy of electron due to electric field too? 2) If yes, how much? I am more interested in second part. Links:Here John Rennie ...
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Why is it that light bends towards gravity when it has no mass at all? [duplicate]

Why is it that light bends towards gravity when it has no mass at all? Is it because of how gravity behaves as mentioned in general relativity? As far as I know, light cannot escape from black holes, ...
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Does a box containing photons have more inertia than an empty box?

A box containing photons gravitates more strongly than an empty box, and thus the equivalence principle dictates that a box containing photons has more inertia than an empty box. The inescapable ...
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Can we produce energy from pure substance having considerable mass? [closed]

According to Einstein's formula, $E=mc^2$. Any substance which has mass can be converted into energy or energy is also existing in the form of mass. So I am very much interested to build a machine ...
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If E= hv then E= mc2 then h=mc2/v! [closed]

E= pc (1) = hv (2), p= mc (3) From (1) and (2): c= hv/p (4) We put (4) in (3): p=hv/p.m => p2=hvm (5) If we use E=hv in (5) we will get: E= p2/m (6) We use (3) in (6) we will get: E= mc2 From ...
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Can a High Enough Temperature Create a Black Hole?

My very basic understanding of GR leads me to think that if a substance has a high enough temperature, it can transform into a black hole without a mass required to create a black hole. The equation ...
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Why does two masses with energy attract each other?

I have heard that every mass attract another mass with a force directly proportional to the multiplication of their masses and inversely proportional to the square of distance between them, but newton ...
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Rainbow Black Hole [closed]

In the photon sphere of a black hole the photons are being trapped in orbit, pulled in and trajectories changed. From a safe distance should we see color from the entire spectrum if light in the ...
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Relativistic Mass and Potential Energy

In the chapter 16–4 of the Feynman Lectures, Feynman employs a thought experiment to explain why "if two particles come together and produce potential or any other form of energy; if the pieces are ...
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Am I just some energy traveled at light speed? [closed]

I don't understand $E=mc^2$ very well, and here is my question: Does this equation mean masses are just condensed energy? And does this mean that the extra energy an object has when traveling at ...
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Einsteins theory of relativity and formula of kinetic energy [duplicate]

After seeing both Einstein's theory of relativity ($E=mc^2$) and the formula of kinetic energy (K.E=$\frac{mv^2}{2}$), I noticed that that they are mostly the same, with the only difference that ...
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Does contracted spring weigh more than stretched one?

(One of examples that potential energy contributes to mass.) Does hot object weigh more than cold one? (One of examples that kinetic energy contributes to mass.) If these are true and justified by ...
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The derivation of the Mass-Energy(including mechanical energy) equivalence principle [duplicate]

(Not duplication! I couldn't find the answer for the general case, instead of the special case that I've already seen in Youtube I hyperlinked.) I will fully satisfy with not only a mathematically ...
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The mass-energy equivalence is a principle which can not be derived from anything? [duplicate]

Not duplication) I couldn't find the answer for the general case, instead of the special case that I already seen in Youtube I hyperlinked. I will fully satisfy with not only a mathematically ...
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The Energy Equation

I've been studying the energy equation in relativistic motion $E= \frac{mc^2}{\sqrt{1-v^2/c^2}}$, which can be expanded as $$E = mc^2 + \frac{1}{2} mv^2\text{ + some other terms.}$$ I'm curious ...