All Questions
Tagged with classical-mechanics statistical-mechanics
189
questions
2
votes
2
answers
316
views
Why does friction tend to slow the objects?
I was biking on the road when suddenly realized a question, that why does friction tend to slow the objects(when the "engine" wasn't doing the "external" work, of course)?
A naive ...
- 3,256
2
votes
1
answer
152
views
Is there a classical limit that connects classical volume/phase space with the scalar product of momentum and position eigenstates?
The book Understanding Molecular Simulation: From Algorithms to Applications, 2002, Daan Frenkel and Berend Smit, states the following
$$
\langle r|k\rangle \langle k|r\rangle = 1/V^N
$$
where $|r\...
- 1,564
0
votes
2
answers
3k
views
What happens when the PE equals to zero in the potential energy vs intermolecular distance graph? [closed]
In the potential energy versus inter molecular distance graph, we know that atoms/molecules/particles want to be at optimum distance from each other ie $r_0$ and to the left of this position in the ...
3
votes
2
answers
214
views
Can every global conservation law be written as following? [duplicate]
Consider a physical quantity $\phi$ that is globally conserved.
From Feynman's argument (in his volume 2 I think), which states that local conservation follows from global conservation due to special ...
- 1,441
0
votes
1
answer
164
views
Derivation of Lagrangian in generalized coordinates
I am reading Mark Tuckerman's Statistical Mechanics and I am going through his derivation of the Lagrangian in generalized coordinates, using the mass metric tensor $G$.
He defines kinetic energy as
\...
- 697
1
vote
2
answers
304
views
Why should layers of air rise up and the layer above it takes it place
I am a high school student and I am very confused in a topic dealing with "why hot air rises up" I know it is already answered but the answers are difficult for me to understand I want a ...
0
votes
0
answers
42
views
Details on why temperature is lower at high altitude
I have read at so many places that warmer air moves up as hotter substances expands and as it rises it loses its kinetic energy and it gets converted into its potential energy(gravitational+...
-1
votes
1
answer
99
views
Calculating the wavelength of vibrations of a material [closed]
I am curious about how you would calculate the wavelength range (the actual wavelength for the particles moving back and forth from their form equilibrium position) for particles vibrating in a solid ...
- 1,896
0
votes
1
answer
17
views
Can gas in a room rotate a fan with asymmetrical spokes?
I was asked this question in an interview. The figure in first part of the question was drawn as shown.
The question was to draw the angular position of the point marked on the rim with time. It ...
0
votes
1
answer
115
views
Deduction of the entropy balance equation with input and output of matter by convection (mass flow)
In many books of Engineering thermodynamics, the entropy balance equation is wrritten as
$\frac{dS}{dt}=\Pi_S+I_S$
$I_S=\sum_{j=1}\frac{\dot{Q}_{j}}{T_j}+\sum_{i=1}\dot{m}_is_i-\sum_{e=1}\dot{m}_es_e$
...
- 3
7
votes
3
answers
1k
views
What is the difference between Liouville's theorem and the Boltzmann transport equation?
From what I understand, Liouville's theorem is about the probability density $\rho$ of an ensemble existing in a differential volume in phase space $d\mathbf{r}d\mathbf{p}$.
So the statement for ...
- 697
9
votes
2
answers
1k
views
Does quantum mechanics halve the dimension of phase space?
In classical mechanics, a particle confined to move along only the $x$-direction can be fully described by a 2-tuple $(x_1,p_1)$ in phase space. In this case, the phase-space is clearly 2-dimensional. ...
- 1,581
1
vote
1
answer
105
views
Why is it said that entropy of a closed system may increase in classical physics?
Why is it said that entropy of a closed system may increase in classical physics?
A classic thought experiment to explain this claim is that of a closed box with some moving billiard balls initially ...
- 676
3
votes
1
answer
666
views
What's the relation of entropy with synchronisation?
2 pendulums tied to a same rod and oscillating with different frequencies and phases synchronize over time. This could be done at home just to see how interesting it is that things try to sync their ...
- 817
1
vote
1
answer
144
views
Notation confusion for differential volume
Can anyone help me with an explanation of the following notation. I am a bit confused:
Lets say we have some type of integral and in the end we write different differential, such as:
$$d\vec r ,\quad ...
- 1,398