Questions tagged [momentum]
In introductory mechanics, the momentum of a particle is its mass times its velocity. In electrodynamics, the momentum of a field is proportional to the cross-product of the electric field with the magnetic field. In special relativity, momentum is generalized to four-momentum.
3,644
questions
1
vote
1
answer
31
views
Energy and momentum conservation for photon absorption [duplicate]
As an undergrad physics student, I am pondering on this question.
If an (2 level) atom absorbs a single resonant photon, the energy of electronic state increases by $\hbar \omega$. At the same time ...
- 11
0
votes
0
answers
39
views
Idealized Newton's cradle
I was wondering about the conditions for an ideal newtons cradle.
Under regular circumstances, the collisions are inelastic and a newton's cradle dissipates energy in various forms like heat, friction,...
0
votes
1
answer
51
views
Why is it less shocking to cross the bump with just one wheel? [closed]
Difference between 'go over speed bump with one side' and 'both sides at the same time'
I asked a similar question previously and received an excellent answer stating that when going ...
- 305
1
vote
0
answers
62
views
Apparent violation of Newton's Third Law in relativistic force transformation
In special relativity, we know that, relativistic force is defined as F = dp/dt, where p = γmv.
For forces perpendicular to the direction of relative motion, force transforms as F' = γF.
Consider two ...
- 5,611
0
votes
5
answers
125
views
Direction of impulse
My textbook has the following problem:
A batsman deflects a ball by an angle of 45° without changing the initial speed which is equal to 54 km/h. What is the impulse imparted to the ball? (Mass of ...
- 342
-3
votes
1
answer
116
views
Noether's theorem by a taste of logic [closed]
I am a mathematician and I asked this question briefly and my question became closed, may be - I don't know - because physicists don't used to apply the method of "proof by contradiction". ...
- 1,409
0
votes
1
answer
28
views
How does the direction of the change in momentum of the object change during the motion?
In the case of an object's movement resembled in this graph, as the gradient is decreasing, a decrease in velocity occurs.
According to the formula
$$p = mv$$,
The momentum is directly proportional to ...
0
votes
1
answer
66
views
Alternative way to compute expectation value of momentum? [closed]
This might be ridiculously incorrect, but is it possible to find the expectation value of momentum like this?
In the position space:
$$\langle x | \psi \rangle = \psi(x)$$
$$\langle \hat{A} \rangle_{x\...
- 11
-3
votes
2
answers
81
views
Meaning of $d\mathcal{L}=-H$ in analytical mechanics?
In Lagrangian mechanics the momentum is defined as:
$$p=\frac{\partial \mathcal{L}}{\partial \dot q}$$
Also we can define it as:
$$p=\frac{\partial S}{\partial q}$$
where $S$ is Hamilton's principal ...
- 443
1
vote
1
answer
69
views
How do you solve instantaneous 3 body collisions
A few years ago I built myself a very basic python program that did some very basic collision mechanics between particles with a mass and velocity and it was helpful in learning a few things and ...
- 111
0
votes
2
answers
83
views
What's the meaning of the momentum operator?
I understand that a wave function $\psi(x, t)$ tells me that the probability to find the particle at position $x$ is $|\psi(x, t)|^2$. In the Schrodinger equation, we use the momentum operator $\hat{p}...
- 11
1
vote
1
answer
88
views
Could we deduce energy, momentum and angular momentum conservation laws from only Galilean relativity?
In Newtonian physics we could deduce conservation of energy, momentum and angular momentum from Newton's three laws.
But by Noether's theorem, conservation laws could be deduced from symmetries.
Could ...
- 1,409
1
vote
0
answers
72
views
Kinematics of a two-body decay [closed]
I suspect a flaw in the reasoning below, but am unable to pinpoint it: Is there something inconsistent in terms of the application of conservation of momentum and energy? Thanks for any hints in ...
- 119
2
votes
3
answers
81
views
Do bodies stick together after an inelastic oblique collision?
My question is particularly about an oblique collision case. (For example a body having velocity along x axis approaching another with velocity along y axis) From what I know, in perfectly inelastic ...
- 41
0
votes
0
answers
33
views
Linearity of Amplitudes and Lorentz Frames
I know that this question may be a bit weird, but I decided to ask. Assume I have an amplitude, say in QED, which depends on a set of four-momenta $\{p_1,\ p_2,\ p_3,\ ...,\ p_n\}$. Further assume ...
- 3,992