All Questions
19
questions
2
votes
3
answers
207
views
Energy and momentum & the relation between them
I am trying to wrap my head around energy, mass and momentum, especially in the more general scope of special relativity where massless objects moving at the speed of light also have momentum. So I am ...
- 219
0
votes
1
answer
35
views
Massive equivalent of a photon and deduction of a photon's linear momentum
Since photons have an energy given by $E=h\nu$, we could define a particle whose rest mass is such that it has the same energy than the photon: $E=m_0c^2 \Longrightarrow m_0=\frac{h\nu}{c^2}$. We now ...
- 1,616
1
vote
3
answers
66
views
Besides traveling at the speed of light, how can we be sure that it is possible to have energy and momentum without mass?
How can we be sure that it is possible to have energy and momentum without mass? If something were to continually lose energy, would it not also lose a corresponding amount of mass? I understand that ...
3
votes
1
answer
233
views
Relationship between mass, momentum and kinetic energy
Is there any fundamental reason why (at least mathematically) momentum is the integral of mass wrt velocity and kinetic energy the integral of momentum also wrt velocity? ie
$$p= \int m \ dv = mv$$
$$...
- 133
1
vote
1
answer
126
views
Why momenergy has magnitude equal to the mass?
The mom-energy of a particle is a 4-vector: Its magnitude is proportional to its mass, it points in the direction of the particle's spacetime displacement, and it is reckoned using the proper time for ...
user307064
-1
votes
1
answer
528
views
Momentum of massless particles [duplicate]
If $E=pc$ for massless particles, then it should be $p=0$ as $p=mv$ and $m=0$. Why do we use the equation $E=pc$ for massless particles?
- 1
0
votes
1
answer
127
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de Broglie wavelength for particles with mass [duplicate]
is $p=\frac{h}{\lambda}$ only true for massless particles? because generally $E=\sqrt{p^2c^2+m^2c^4}$, then if we equate it to $h\nu$ we get $$p=\sqrt{\frac{h^2}{\lambda^2}-m^2c^2}\neq\frac{h}{\lambda}...
- 1,038
0
votes
3
answers
180
views
Do photons really have kinetic energy?
I haven't found a satisfactory answer to this question.
In special theory of relativity
$$E=\sqrt{m_{0}^2c^4 + p^2c^2}.$$
When we consider photons where $m_{0}=0$ then $E=pc$ but we also know that ...
- 3,377
4
votes
4
answers
2k
views
Ultra-Relativistic and Non-Relativistic cases for energy of a particle
Let us suppose that we have a particle of energy $$E = (m^2c^4 + p^2c^2)^{1/2}$$
Can we say that for ultra-relativistic limit $p \rightarrow \infty$
$E = pc$ ?
Or in the non-relativistic case $p ...
- 3,122
0
votes
1
answer
71
views
Energy and momentum
Does a muon or an electron with the same energy have the higher momentum?
According to $E^2=m^2+p^2$ if you increase the restmass, the momentum must decrease.
But if we look at a nonrelativistic case:...
- 109
13
votes
2
answers
2k
views
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 ...
- 357
0
votes
0
answers
92
views
Derivation for relationship between rest mass, kinetic energy and momentum
I am trying to find a particle's rest mass in terms of its kinetic energy and momentum. Is this following derivation correct?
$(E_{0}+K)^2=E_{0}^2+(pc)^2$
$2E_{0}K=p^2c^2-K^2$
$2m_{0}c^2K=p^2c^2-K^...
- 155
2
votes
5
answers
3k
views
Conservation of mass in relativistic collisions?
It's stated in my textbook that relativistic mass is conserved in collisions, even in inelastic ones. So if you have a particle with rest mass $m$ moving with speed $u$ (considerable fraction of the ...
- 1,307
1
vote
5
answers
83
views
Distinction between various forms of relativistic energy
If I am told to find the total relativistic energy of a particle moving with some velocity v, do I use $E=\gamma mc^2$ or $E^2=p^2c^2+m^2c^4$ and take the square root. I am not sure the distinction ...
user206026
2
votes
5
answers
3k
views
Derivation of $E=pc$ for a massless particle?
In classical mechanics, massless particles don't exist because for $m=0$, $p=0$.
The relativistic relation between energy, mass and spatial momentum is: $E^2= (pc)^2 + (mc^2)^2$ . So it is said that ...
- 121