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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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Bare Critical Masses of $^{241}$Am, $^{242m}$Am, $^{238}$Pu and $^{242}$Pu

$^{238}$Pu has 144 neutrons, and it has 2.8$\times$10$^{3}$ g$^{-1}$.s$^{-1}$ spontaneous fission neutrons and bare critical mass in 10 kg. $^{242}$Pu has 148 neutrons, and it has 1.7$\times$10$^{3}$ ...
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Is the potential energy of falling into a black hole already included into E=mc^2?

Each object in the Universe has a huge potential energy, because you can drop it into a black hole, accelerating it to nearly the speed of light. Is this potential energy already included into ...
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How to derive: $\frac{E^2}{c^4} = \frac{p^2}{c^2} + m_0^2$?

My teacher wrote the following equation on the board a few days ago: $$\frac{E^2}{c^4} = \frac{p^2}{c^2} + m_0^2$$ And I got no idea how this is derived especially since we already derived that: $$m^...
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Why is the actual KE value smaller than what I calculated?

Problem The nuclear equation for the decay of calcium-47 into scandium-47 is given by: The following data are available: Mass of calcium-47 nucleus = 46.95455 u Mass of scandium-47 nucleus = 46....
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Fusion Kinetic Energy

In fusion, the mass of the reactants is greater than the mass of the products. Thus, mass is lost in fusion. My thinking was that this mass defect is converted into binding energy that is then used to ...
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Composite objects, mass, and internal energy in relativity

Why do we define the free Hamiltonian of composite particles as $$H_0 = \sqrt{M(t)^2c^4 + P^2c^2}$$ with $M(t)\neq\sum_im_i$ instead $$H_0 = \sqrt{M^2c^4 + P^2c^2} + U(t)$$ with $M=\sum_im_i$ and $...
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Why does stability come from binding energy and not mass

The mass of a nucleus is given by: $$ Mc^2=n M_n c^2+zM_pc^2-B(z,n) $$ And we were told that nuclei want to maximise the binding energy per nucleon. However, I don't see why they don't want to ...
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What is the relativistic mass of Red Light? [duplicate]

After using all the equation and formula's I am getting Light has a certain mass, i.e. 3.157x10^-36 (approx) Kg. Then I have calculated the Energy by using the famous equation, i.e. the E=mC^2 (In ...
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Basic Question on Black Holes and the Potential Loss of Conservation of Energy/Mass [duplicate]

I am reading Kip Thorne's "Black Holes and Time Warps" and I have a basic question on a topic he is discussing while talking about Einstein and Eddington's disbelief in black holes. So the general ...
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How we can prove that photons have no mass? [duplicate]

I am thinking nowadays that how its possible that a particle without mass, actually exists? in the case of light its used to say that photons have no mass no weight but they have momentum. can any ...
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Is this relativistic mass?

I have seen in a lot of places in here clearly stating that relativistic mass is outdated, that we can make do just fine with the concept of invariant mass,etc. But I've also seen people saying that a ...
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Is there an example of two elementary particles colliding to result in a single elementary particle?

Apologies for the novice question, but I don't know enough particle physics to immediately answer my own questions. I have the following questions. Is there an example of an inelastic collision ...
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Why is energy released during fission reactions?

If the energy released during a fission reaction is the binding energy then what energy is left to bind the nucleons together? I'm very confused if there's a better explanation on fission I'd ...
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What exactly is binding energy?

I've been reading on radioactivity but along the way I got confused, if binding energy is the amount of energy used in holding the nucleus together then why is binding energy also the amount of energy ...
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What exactly is binding-energy? [duplicate]

I was reading on radioactivity, and I got really confused along the way. If you want to combine two things together, you have to supply some energy in pushing them towards each other, and the energy ...
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Are energy and mass two forms of the same thing?

I know that energy can convert to mass and vice versa. So are we not looking at simply two forms of the same thing?
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Does the relation between energy and mass, proposed by Einstein hold true for all forms of energy? [duplicate]

I don't have a strong chemistry background, but I recently stumbled upon an answer that concluded that when supplying a reactant(s) with energy E it should be that the difference between the masses of ...
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If a black hole is created from light, can this black hole then move at the speed of light?

Imagine we managed to squeeze light into a very tiny region of space so that the energy concentration at that point becomes a black hole. Can this black hole then move at the speed of light?
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How to calculate energy loss of falling object [closed]

I've done an experiment where I dropped 3 balls from a meter high and I want to record the energy loss they get once they bounce. I have height measurements for the first fall and the bounce. How ...
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Why do we say that a photon is a particle if it is massless?

If light is made of photon particles and the photon doesn't have any mass but it is a form of energy (according to my thinking) then why do we call photons particles?
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Would inspiraling binary wormholes produce gravitation wave?

Mathematically I am wonder would two binary wormholes radiate intense energy as gravitational wave as they get closer and closer together, I like to know what happens to the mass (or negative mass) ...
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Is the warping of spacetime proportional to the mass/energy/momentum of an object in GR [duplicate]

Just wondering if the warping of spacetime proportional to the mass/energy/momentum of an object in general relativity?
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Can a Spaceship decelerate by increasing its mass?

Suppose the following thought experiment: A spaceship travels at speed u and has mass m. At a point, it converts massless or low mass particles, that it "carries", to heavier particles without any ...
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What happens to the energy of an absorbed photon?

Photons are electromagnetic wave fields that travel at the speed of light. When they are absorbed by an object, their momentum and energy is transferred to the absorbing object. What is that ...
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Does charge affect space-time?

Okay suppose there is an hypothetical particle called Nelectron which has mass = mass of electron but is electrically neutral. It has same spin and other quantum mechanical properties. Even the same ...
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Confusion regarding conservation of momentum and conservation of energy [closed]

When solving the problem under in the two different ways listed, i end up getting different answers. An electron is moving with $v_1=0.87c$ perpendicular to a positron moving with $v_2=0.98c$ in an ...
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How is mass of neutron compared with proton when it is inside the nucleus? [closed]

The mass of free neutron is around 0.1% more than the mass of proton. When it is bound inside the nucleus, neutron mass is less compared to its mass in free state. The question is how much mass it ...
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Total mass-energy of a system in GR [duplicate]

the Gravitation book confirm that "for closed universe the total mass-energy and angular momentum is undefined and undefinable" why many cosmologists claim that the total energy of a closed universe ...
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If matter comes from energy, does this mean that energy has weight?

If the matter in the Universe formed from the energy of the Big Bang, and matter has weight, does this mean that energy has weight? Moreover, as the Universe expands over time, does its overall ...
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Derivation of Komar formulae from ADM formalism?

Is there a way to derive the Komar formulae from the ADM formulae? Both the formulae give the same answer for mass and angular momentum, so I was wondering if one can be derived from another. On an ...
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Conservation of Mass and Energy [duplicate]

I was thinking about some physics (relativity in particular), when it suddenly occurred to me that all my life I had been balancing chemical equations assuming conservation of mass, but I was ...
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About nuclear energy levels

The energy level of a heavy atomic nucleus such as that of uranium, which is related to the zeta function, is determined by taking a discrete value, but cannot it be represented by an equation like an ...
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Do black holes violate the conservation of mass?

This question has confused me for quite some time now. I have searched it up online, and the basic answer is: 'Mass is a form of energy. When black holes die they release the amount of energy that ...
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Do photons have any relativistic mass?

In some books I found they are writing photon momentum $mc$ rather than $E/c $. Which one is right? But if I put $v=c$ in relativistic mass equation, $$m=\frac{m_0}{\sqrt{1-v^2/c^2}},$$ it becomes ...
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How is mass defined by special relativity?

I am eagerly interested in all kinds of areas of physics. As the question of mass has been around for a pretty long time, I am interested about what modern physics namely special relativity says about ...
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Special relativity - mass energy and momentum [closed]

I've just started studying relativity and I think I have just about gotten my head around time dilation and length contraction and I have now been able to derive the two equations $$t=\frac{t_0}{\...
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Mass-energy equivalence and heat capacity

From Wikipedia: Einstein's mass–energy equivalence states that anything having mass $m$ has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one ...
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Mass-energy equivalence - old notation

Einstein originally gave the formula as $$M = \mu + \frac{E_0}{c^2}.\tag{17}$$ In which $\mu$ was the mass of the system. Today, we more commonly get taught that the energy is in relation to the ...
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How can one define a covariant rate of change of rest mass for an extended body?

For a point mass I can define a covariant rate of change of its rest mass as $\frac{d}{d\tau}m_0$ where $\tau$ is the proper time. How can I also define a covariant rate of change of rest mass for an ...
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How is rest mass $m_0$ in $E=m_0c^2$ related to mass $m$ in $F=ma$?

A particle at rest has energy given by $$E=m_0c^2$$ where $m_0$ is defined as its rest mass. So rest mass is essentially a measurement of a particle's intrinsic amount of potential energy. How is ...
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Density $\rho$ in the Friedmann equations

In the Friedmann equations: $$\ddot{a}=-\frac{4}{3}\pi G(\rho+\frac{3p}{c^2})$$ $$\dot a^2+Kc^2=\frac{8}{3}\pi G\rho a^2$$ I didn't understand if $\rho$ is the mass density deriving from $m_0$ (the ...
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Thermal energy turning into mass?

When you heat an object it's mass increases $E=mc^2$. What I don't understand is that this energy can be converted to mass and still be thermal energy too (object still hot). When a radioactive ...
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Impact of electronic binding energies on mass

According to relativity, the inertial mass of an object that enters into the force equation to get acceleration is given by the total energy in the center of mass rest frame. $$E=Mc^2=\sum_i (m_i c^...
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Energy-momentum relation in SR and GR

There is the famous energy-momentum relation $$E^2 - p^2 c^2 = m^2 c^4.$$ I thought it is always valid. "Always" means it is valid in general, so in GR and SR. It is something like an elemantary ...
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Local mass function in spherically symmetric spacetime

I am studying the paper `Inflation and de Sitter Thermodynamics' at https://arxiv.org/abs/hep-th/0212327 . I have problems with the way they define a local mass function in a general spherically ...
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Do variations of the Earth's magnetic field affect gravitational acceleration at Earth's surface, and if yes, by how much?

The Earth's magnetic field varies with time over geological time scales (we have phenomena such as pole inversion). Can this affect the acceleration of gravity at Earth's surface? I would think that ...
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Energy and mass at absolute zero temperature

Hi my question is if the temperature of a particle is reduced to absolute zero the that particle has lost its energy so it has no movement. Particles have mass and Einstein said mass equates to energy....
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Does the gravitational field possess an inertial mass? [duplicate]

I understand that inertial mass, at least in part, comes from the inertia of energy in the zero momentum frame or rest frame of some physical system. So for a static charge the corresponding field ...
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Mass and Energy conversion in photon

If energy can be converted into mass then why isn't photon's energy being converted into mass?
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Why do fusion and fission both release energy?

I only have high school physics knowledge, but here is my understanding: Fusion: 2 atoms come together to form a new atom. This process releases the energy keeping them apart, and is very energetic. ...