Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [kinetic-theory]

Kinetic theory is part of statistical physics. DO NOT USE THIS TAG for macroscopic kinematics. In this case, use the tag [tag:kinematics] instead.

0
votes
0answers
23 views

Energy loss of gas due to Collisions [on hold]

A large number of identical elastic balls are moving randomly in a fixed vertical cylinder under a piston that is at height H above the bottom of container. The container is kept in a gravity free ...
-3
votes
2answers
51 views

Compression of gas [on hold]

What happens when a gas kept in a metallic container is suddenly compressed via a piston and left for some time? Does the pressure increase or decrease?
0
votes
1answer
42 views

How was Maxwell able to derive velocity distribution? [on hold]

Did he assume that their velocities follow some kind of statistical distribution and fit the parameters accordingly. Or did he mathematically prove it?
1
vote
1answer
21 views

Vrms for monotomic, diatomic, and polyatomic molecules

in my notes from class I have that Vrms= sqrt(3kT/m) for a pt molecule Vrms= sqrt(5kT/m) for a diatomic molecule and that Vrms= sqrt(6kT/m) for a triatomic-> higher order molecule but RMS Speed of ...
0
votes
0answers
25 views

Reverse engineering Newton's approximation of impact depth

I recently learned about Newton's approximation of impact depth, Depth = (Projectile Density / Target Density) * Length of the projectile. Where length and depth is measured in meters, and density is ...
0
votes
0answers
17 views

Why is the electric current is a scalar quantity? [duplicate]

Please help me because I didn't know why. If you know please help me!!
0
votes
0answers
14 views

Is there any equation to calculate water vapor condensation?

Basically, I can to calculate the mass of water accumulated on a surface at a given time if the surface is exposed to Room temperature keeping its temperature let say -25 C. Any help will be ...
0
votes
2answers
52 views

Kinetic Theory of Solids

Is there a clean way to examine temperature for solids and liquids in classical mechanics like the kinetic theory for gases? I'd like to get a good explanation that doesn't involve much in the way of ...
1
vote
1answer
29 views

A hypothetical scenario regarding the pressure exerted by an ideal gas on the walls of a container using kinetic theory

This is a question I came across recently : "1 mole of an ideal gas is contained in a cubical vessel of volume V, ABCDEFGH (these are the vertices of the cube). One of the faces of the cube EFGH is ...
0
votes
0answers
28 views

Kinetic theory postulates and Van der Waals

What was the purpose to assume that gas molecules are point particles? What could be explained through this postulate? Also when we refer to kinetic theory the postulates of this theory are the ...
1
vote
1answer
61 views

Estimating the inter-molecular van der Waals' force from the boiling point of water

Background: I understand that inter-molecular van der Waals' forces are responsible for maintaining water in the liquid phase. Now, if we suppose that the net van der Waals' force on a given H2O ...
0
votes
0answers
23 views

Entropy in the Klimontovich Picture of Kinetic Theory

In the Klimontovich picture of kinetic theory, a classical $N$-body system is fully specified by the phase-space distribution $$ \rho(\vec X,t) = \sum_{i=1}^N\delta[\vec X-\vec X_i(t)] , $$ where $\...
8
votes
2answers
146 views

Rigorous derivation of the mean free path in a gas

Can anyone supply me with a derivation of the mean free path, of particles in a Maxwell Boltzmann Gas? Cited in various literature is the formula, \begin{align} \begin{split} \ell&=\frac{1}{\...
0
votes
0answers
32 views

Solution of the diffusion equation in a plasma

considering the diffusion equation taking into account diffusion and mobility of charged particules in a plasma of density $n(z)$ and potential $\phi(z)$, we have : $$ \frac{n(z)}{\tau}=\frac{\...
2
votes
2answers
52 views

What is temperature as a function of time in Fourier's Law?

Can we find temperature as a function of time using Fourier's Law of thermal conduction? For example: If we have two square parallel plates of a given length, width, and distance apart with one ...
0
votes
1answer
22 views

Is the rate of nucleation of bubbles in beer dependent on the temperature of the liquid?

Since there's more energy in the fluid, I believe that you will have a higher nucleation rate in a hotter (assuming all other relevant variables remain unchanged), is this the case? How can I ...
0
votes
0answers
26 views

What are the specific heats of Dysprosium in its gas phase?

What are the specific heats of Dysprosium in its gas phase? The handbook of chemistry and physics [1], is a single volume of 1500 pages containing all the information an experimentalist would need ...
1
vote
1answer
23 views

Reconciling various expressions of flux and flow in kinetic theory

There are a few expressions I have been shown to describe the flux $\vec{\Phi}_A$ of some quantity $A$ described in kinetic theory. I am having trouble understanding how they are related or if they ...
2
votes
2answers
57 views

Why gas molecules move with different speed at a given tempreture?

As per my understanding we know that molecules of an ideal gas are identical in all aspects (size, shape, mass). Since collisions are elastic in nature, they don't lose their kinetic energy. That ...
-1
votes
0answers
60 views

Derivation of the Euler fluid equation

I'm currently taking a class on Thermodynamics where we now briefly touched upon Hydrodynamics. On of the major points of the chapter is deriving the Euler fluid equation and there I found my self a ...
0
votes
2answers
38 views

Air temperature equilibrium

Suppose an ideal airtight room, filled with air, no changes in volume, amount of air or energy. On the one hand, "hot air rises" (less dense, flotation, convection...) ((there's gravity, we are on ...
0
votes
1answer
33 views

Boltzmann equation derivation for $H=v\sigma \cdot p$ hamiltonian

I am trying to write the Boltzmann equation for $$H=v_{F}\vec{\sigma}\cdot(\vec{p}-e\vec{A}).$$ This is a free charged particles gas. The velocity for this hamiltonian is $$\vec{v}=v_{F} \vec{\sigma}.$...
1
vote
1answer
60 views

Angle of particles hitting a wall - Kinetic theory of gases

In Blundel's "Concepts of thermal physics" it says that the number of particles hitting a wall with speeds between $v$ and $v+dv$ and angle between $\theta$ and $\theta +d\theta$ to the normal of the ...
0
votes
0answers
20 views

Difficulty in calculating effusion rate using the kinetic theory of gases and statistical mechanics

I have tried multiple sources and methods, but my attempts at a proof of the number of particles leaving a gas using statistical mechanics keep finding the same wrong result. I have tried to read ...
1
vote
1answer
32 views

Confusion while deriving kinetic-molecular theory of gases

How many of the molecules will collide within a given area A of the wall normal to the x-direction in some fixed time interval Δt ? On average half the molecules have a positive x-...
0
votes
1answer
18 views

Reconciling two views of Matthiessen's rule for electron mobility

My understanding of Matthiessen's rule is that when electron conduction in a solid is inhibited by more than one mechanism, that the overall resistivity $\rho$ is formed as if these resistance source ...
0
votes
1answer
80 views

Help me in understanding the general principles behind evaporation and condensation of a liquid

I will place my two questions infront of you guys. Let's consider the liquid is water. 1) " How and why exactly does water vapor in air condense at the surface of water? Is vapor in air condensing at ...
3
votes
3answers
160 views

What underlying physical quantity do we measure when measuring the temperature of gases?

When we measure the temperature of, say air, or any other gas, what physical quantity do we measure? Is it the kinetic energy of molecules? Is this affected by pressure and density? And if so, how?
0
votes
1answer
435 views

How can I Derive the Equation for Coefficient of Linear Thermal Expansion?

I know the relationship between change in temperature and change in length. When the ambient temperature around any substance is increased, its length increases. This is due to molecules gaining more ...
2
votes
0answers
28 views

Time symmetry of Boltzmann kinetic equation and H-theorem for calculating time-evolution of entropy

I know the Boltzmann kinetic equation is invariant under T transformation ($t \rightarrow -t$). Also, I could derive the entropy's time evolution from H-theorem as: $$\frac{\partial S}{\partial t} = -...
3
votes
2answers
238 views

Difference between pressure and temperature

If I am given the average kinetic energy of the molecules of a gas or a liquid, how can I tell if the fluid will burn me/crush me/both if I immerse my hand in it? Equivalently, what is the difference ...
0
votes
1answer
41 views

How far does a teflon ball roll on a very even surface? [closed]

As teflon has a minimal frictional coefficient of about 0.04, how far does a ball made of teflon roll on a even surface in comparison to another ball (made of wood or iron, for example), when pushed ...
0
votes
1answer
159 views

2 Extra Degree of Freedom in Linear Triatomic Molecules?

Ok, there is a bit problem in understanding Degree of Freedom of Linear Molecules specially of Triatomic Linear Molecules. See, the DOF in general is given as $f=3N-k$. Here, N=Number of atoms in a ...
1
vote
0answers
26 views

Derive total energy balance equation from Chapman-Enskog analysis of lattice Boltzmann equation

I'm interested to derive the total energy balance from Chapman-Enskog analysis of lattice Boltzmann equation (LBE). I know, I should go to the second moment of LBE (zeroth moment gives mass ...
3
votes
2answers
85 views

Why does frequency of collision increase as volume decreases?

Today I was presented with the following scenario: A syringe with one end sealed and with a frictionless piston is dipped into cold water. What is the change in frequency of collision(ie, more or ...
2
votes
1answer
70 views

What is kinetic theory?

What is kinetic theory? I am taking a course on fluid dynamics right now, and I have been wondering about one thing for some time now. We have three ways to look at a gas ($N$ particles): 1) ...
0
votes
1answer
36 views

anistropic or asymetric particles distribution

As a preamble, I have several questions and I know that is preferable to ask one question per post, but they are really linked together. This is why I chose to ask them together. I am considering a ...
0
votes
1answer
35 views

Temperature relaxation from kinetic equation

Suppose we have the kinetic equation $$ \frac{\partial f}{\partial t}=-\frac{f-f_0}\tau $$ for the electron distribution function in momentum space $f(\mathbf{k},t)$. Here $\tau$ is the relaxation ...
2
votes
2answers
218 views

Actual Degree of Freedom of Diatomic Molecule

Ok, I have 2 very different values for degree of freedom(DOF) of diatomic molecules arising due to the difference in the vibrational DOF of the diatomic molecules. According to this DOF wiki page:- ...
0
votes
1answer
34 views

Is it possible to change the pressure of a gas at constant volume without increasing the temperature?

$v_{rms}$ of an ideal gas is given by $\sqrt{\dfrac{3RT}{M}}$ . Now I believe that this depends only on temperature and molar mass of the gas. But someone told me to write RT as $\dfrac{PV}{n}$, then ...
1
vote
3answers
186 views

Temperature of the system stays constant even though it moves? [duplicate]

According to thermodynamics we were taught that temperature of a body is the measure of avg kinetic energy of the molecules which make up the body . Now if we consider an insulating box full of gas at ...
1
vote
2answers
67 views

What causes the distribution of energy among molecules?

If every molecule were to start of with the same kinetic energy would it become a distribution of energy like the boltzman distribution and if so why? Is it due to inelastic collisions?
0
votes
2answers
99 views

Pressure change during free expansion of an ideal gas

In free expansion W=0, even though volume changes and if q=0, then temperature and internal energy do not change. But what about pressure? I will present some arguments, please tell me which one(if ...
0
votes
0answers
25 views

Entropy production during leptogenesis

Do the out of equilibrium decays of right-handed neutrinos in standard leptogenesis scenarios lead to a net entropy production? Does this entropy production lead to observable effects (like reheating)?...
0
votes
2answers
62 views

Temperature dependence of elastic collision of gas molecules with the wall

The following is written in my textbook and I quote it here The collisions of gas molecules with the walls are elastic of the temperature of the walls is same as the temperature of the gas. I am ...
0
votes
1answer
32 views

Is mechanical equilibrium assumed while finding the equation of state in thermodynamics?

The mechanical equilibrium is a state in which the pressure (and elastic stress) inside a gas is evenly distributed. Do we make such an assumption while deriving the equation of state in ...
1
vote
1answer
44 views

Boltzmann's papers [closed]

I wonder if anyone knows where i can find the main papers of Boltzmann translated in English. Especially his monumental work on 1877 "On the Relationship between the Second Fundamental Theorem of ...
0
votes
1answer
50 views

Time required for change the momentum of a gas molecule in a cube

In a cube with side length L, consider a gas molecule with x-component of velocity being $C_x$. The question arises while dealing to calculate rate at which molecule transfers momentum to the wall. ...
0
votes
1answer
50 views

Kinetic Theory Proof

How would I prove that the number of collisions by gas molecules on a wall of unit area per unit time is $r = \frac 1 4 n \left< v \right>$ using the Maxwell-Boltzmann speed distribution ...
0
votes
1answer
34 views

How to calculate mean velocity of gas particles along some line of sight in a simulation?

In a cosmological hydrodynamic zoom-in simulation, we happen to know both the position and 3d velocity of gas particles in the simulated volume. However, I am interested only in a column of gas along ...