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Questions tagged [kinetic-theory]

Kinetic theory is part of statistical physics. DO NOT USE this tag for macroscopic kinematics; use the [kinematics] tag instead.

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Relation between electron temperature and electronic mode of energy for a gas

I have been doing some introductory reading on plasma physics as part of my research, and I am currently trying to understand the concept of electron temperature. Based on my basic understanding, ...
Nikkhil Chander's user avatar
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Why should the rate of evaporation of liquids depend upon the rate at which the molecules strike the surface?

This paper says: The development of the kinetic theory of gases led to the conclusion that the maximum rate at a particular temperature would be given by the rate at which molecules strike the ...
Ritesh Singh's user avatar
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1D Ring Ising model with kinetic rates

I have a system of $N$ spins on a ring which undergo linear kinetics. the spins can assume values of 0 and 1 (super important). The dynamics of each spin correspond to $\frac{dn_i}{dt}=k_{on}(1-n_i)-...
jarhead's user avatar
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During evaporation, why would we expect temperature of the gas at the interface to be lower than the temperature of the liquid?

This paper says that, from the kinetic theory of gases, we expect temperature of the gas at the interface to be lower than the temperature of the liquid. Could the experts here please explain it? ...
Ritesh Singh's user avatar
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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 ...
Max's user avatar
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Why the work done by surrounding on the piston is same as average work done by surrounding on the gas inside the cylinder? [closed]

In thermodynamics when we derive the formula for work done by the surrounding on the gas, we actually derive the formula for work done by the surrounding on the piston and say that let the surrounding ...
Virender Bhardwaj's user avatar
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Can the Boltzmann distribution function apply to liquids? [duplicate]

I have been searching for ages about any way that I can calculate the kinetic energy or particle speed of liquid molecules, but all I can find are gas laws. I'm trying to calculate the probability of ...
Abigail Mckinnon's user avatar
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Assumption of molecular chaos (confusion)

The molecular chaos means that the velocities of the two particles are uncorrelated before the collision. However, this is no longer the case after the collision, which is why the whole problem with ...
Raul E.'s user avatar
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Derivation of the Coulomb Collision Operator for Plasmas

I am attempting to learn about Coulomb collisions in the kinetic theory of plasmas. In doing so, I have come up with an "intuitive" derivation of a Coulomb collision operator. However, the ...
MeowBlingBling's user avatar
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Mean free path equation for plasma

Does the mean free path equation $$\lambda=\frac{1}{\sqrt{2}\pi d^2 n_v}$$ work for collisions in plasma or just for gas?
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Has any work been done to describe the transient behaviour of a non-uniform ideal gas in an adiabatic process?

Recently, I've come across a discussion where a person believed classical thermodynamics predicted loss of energy in free expansion. After discussing for a while, I found out that that person made a ...
ioveri's user avatar
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Cohesion forces and evaporation due to pressure reduction

So, we all know that there are two ways to evaporate a liquid, either by increasing its temperature through heating, which could be explained microscopically, as we're providing the molecules of the ...
Mark Spencer's user avatar
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Apparent inconsistency with Maxwell-Boltzmann energy distribution

The Maxwell-Boltzmann distribution for the kinetic energies of particles is given as ( https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution#Distribution_for_the_energy ) $$f(E) = 2 \...
Thomas's user avatar
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Energy distribution of water molecules without considering the free gas hypothesis

considering water molecules as a free gas at a certain temperature, their kinetic energy distribution is given by the Maxwell-Boltzmann distribution (associated with temperature), right? So, if I want ...
tchitchas's user avatar
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When is a Schrodinger equation equivalent to a Fokker-Planck equation?

In chap. 3 in these notes on kinetic theory, Tong shows that the Fokker-Planck operator for a particle undergoing overdamped Langevin dynamics in a potential $V$ is equivalent to a Schrodinger ...
Panopticon's user avatar
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In the molecular kinetic theory of gases, why do the magnitudes of the forces for each molecule add directly?

Should there be a decomposition of the vector components to consider the component perpendicular to the wall and then perform a vector addition? In other words I don't understand why the total force ...
Time Step's user avatar
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How can the magnetic mirror force act along B direction if it is derived from $q\vec{v} \times \vec{B}$ force?

A typical derivation of the magnetic mirror force of a charged particle in a magnetic field such as from Nicholson (1983) pg 26 uses the $q \vec{v} \times \vec{B}$ force, conservation of the dipole ...
E. Nerney's user avatar
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Temperature too high in kinetic gas theory experiment with steel balls

I'm doing a small experiment about kinetic gas theory where I have to check if the density of my gas corresponds to the barometric formula. My experimental setup is like this one Experimental setup ...
Guillermo Fuentes Morales's user avatar
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How is number of collisions per unit distance related to mean free path?

Recently I have been studying Kinetic Theory Of Gases, with one of the topics as collision frequency. I know that collision frequency is inverse of relaxation time which is also the measure of number ...
Ankita Bharati's user avatar
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Work done in an elastic collision in the following case

In a perfectly elastic collision the two bodies that collide will end up maintaining their complessive initial momenta and kinetic energy. Basically if body A impacts against body B at 10 m/s (with ...
Riccardo Zanardi 's user avatar
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Definition of injection spectrum of an electron beam

Referring to Plasma Astrophysics, Part 1, Eq 4.32, The number density of electrons in the beam at a distance $z$ from the injection plane at $z = 0$ is defined as, $$ n_b(z) = \int_{0}^{\infty} \int_{...
Refrigerator's user avatar
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Derivation of pressure in the kinetic theory of gases

According to Wikipedia, The pressure exerted by the collisions of the N gas particles with the surface can then be found by adding the force contribution of every particle and dividing by the ...
Boar's user avatar
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How can I determine sound speed of ions in plasma sheath

Since the definition of sound speed, ($c_{s}$), in each ion s$th$ species ($is$) expressed that: \begin{align*} c_{s,is} = \sqrt{\frac{k(T_{e}+T_{is})}{m_{is}}}. \end{align*} How can we determine ...
nirama_xox's user avatar
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Derivation of kinetic equation for fast particles in a plasma

Referring to Plasma Astrophysics, Part 1, author: Boris V Somov, 4.1.1, We have the kinetic equation with Landau collisional integral, $$ \frac{\partial f}{\partial t} + v_{\alpha} \frac{\partial f}{\...
Refrigerator's user avatar
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Does temperature only depend on the translational kinetic energy of a molecule? [duplicate]

SO, I think we define temperature as something related to the average translational kinetic energy of a molecule. Is temperature dependent on the rotational and vibrational energy of the molecules. If ...
The Interpreter's user avatar
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Why is temperature a " Frame independent " quantity? [duplicate]

The fact that if we place a jar full of gas in a moving train won't change its temperature , and that the temperature isn't really affected by the motion ( even though kinetic energy of gas molecules ...
The Interpreter's user avatar
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117 views

Dynamic of Alfvén waves in a hot magnetized plasma

I'm trying to derive the dispersion relation of Alfvén waves (AW) by solving analytically the Vlasov-Maxwell equations for a magnetized hot plasma but I'm confused. A simple question, to treat AW ...
Gallagher's user avatar
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Absolute Angular Velocity - How to use?

From my dynamics course, we were introduced to the so-called absolute angular velocity of a rigid body. Below is a short diagram: The following equation for the velocity of point P on a rigid body is ...
user393495's user avatar
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1 answer
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Definition of temperature as variance of the momentum

I have always taken the definition of temperature to be the kinetic energy Statistical mechanics definition of temperature as the average kinetic energy. However I have been reading a paper where the ...
Daniel Adams's user avatar
1 vote
1 answer
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Does Andrews curve's density in Liquid- Saturated vapor phase change region vary or not?

Are Andrews Curve (isotherms) for gas-liq phase change less dense for low values temperature and more dense for high value of temperature? I came up with this because of Clausius Clapeyron Equation ...
SHINU_MADE's user avatar
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Validity of $C_p-C_v = R$

This might be a very novice question but i got confused over derivation of $C_p-C_v = R$ which is derived using $dQ= n C_p dT,$ which is valid only for isobaric process. Thus $C_p-C_v = R$ must also ...
SHINU_MADE's user avatar
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Clarification regarding 'Boyle's Temperature' definition

In the Boyles law def- "The temperature at which a real gas obeys ideal gas law over an appreciable range of pressure is called Boyle temperature." Why "over an appreciable range of ...
SHINU_MADE's user avatar
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Mach number: understanding incompressibility through acoustic time scale

In the past I have always recognized the mach number as being the ratio between the bulk velocity of a fluid $v$ in relation to the speed of sound in that medium. I have also seen how one can derive ...
Tanamas's user avatar
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A question based on the kinetic theory of gases

An insulated container containing monoatomic gas of mass $m$ is moving with a velocity $v$. If the container is suddenly stopped find the change in the temperature of the gas. I want to know why ...
NAITIK VERMA's user avatar
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What would be the pressure, temperature and density gradients with altitude of atmosphere with ideal gas?

What would be the pressure, temperature and density gradients with altitude of atmosphere with ideal gas considerations? That is no convection or radiation. Most of the answers I have seen are ...
Rejeev Divakaran's user avatar
1 vote
0 answers
69 views

Most probable velocity of a mixture of gases [closed]

We have the average, root mean square, and most probable velocities of a gas as $v_{av}=\sqrt\frac{8KT}{\pi m}$ ; $v_{rms}=\sqrt\frac{3KT}{m}$ ; $v_{mp}=\sqrt\frac{2KT}{m}$ For a mixture of two ...
Chirag Swarnkar's user avatar
2 votes
2 answers
105 views

How do kinematic equations work regardless of mass of the object?

I came across this question (very simple): "A dog is running and starts to get faster at $2 ms^{-2}$ for $3s$. If the dog covers $20 m$ over this time, what velocity did it start with?" ...
fastandcurious's user avatar
2 votes
0 answers
44 views

Definition of temperature in Boltzmann transport theory

In kinetic theory, the local temperature in a fluid is defined in terms of the average thermal energy of the particles, as \begin{equation} \langle E_{th}\rangle= \int {d^3v}\frac{1}{2} m|\mathbf v-\...
Ramal Afrose's user avatar
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3 answers
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Doubt regarding kinetic theory of gases

My school teacher had told me that one of the assumptions of Kinetic Theory of Gases was that the molecules of a given gas were all identical and to be considered as very small elastic spheres. ...
Rexquiem's user avatar
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Why expansion of real gases lead to cooling?

Paul Hewitt writes in his book Expansion of real gases lead to cooling as average translational kinetic energy per molecule decreases. The reason given is: During Expansion molecules collide with ...
Shinnaaan's user avatar
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Vibration modes and specific heat for $CO_2$ [duplicate]

I'm having a confusion regarding the molar specific heat (at constant volume) for the carbon dioxide. Suppose we admit that this quantity is related to the degrees of freedom of the molecule by the ...
Johann 's user avatar
2 votes
1 answer
57 views

Measuring thermal conductivity

Suppose we have a long, cylindrical, wire of radius $a$ and a resistance $R$ (per unit length), which is laid out along the axis of a hollow cylinder of radius $b$, which is kept at a fixed ...
Adrien-Marie Deschamps's user avatar
1 vote
1 answer
30 views

Collision frequency of a 3D object in a container

Might be a silly questions but I had a thought while learning about the collision frequency of gas molecules on a single surface of a container using kinetic theory. For a 3D object in the container, ...
Yourhelpismuchapprecciated's user avatar
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1 answer
47 views

Why is friction positive in this solution?

According to the solution, the work of kinetic friction is positive, but doesn't the friction force always go negative to the displacement, making the work by friction negative? Why is friction ...
Am001's user avatar
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Mathematical modeling of low-temp plasma

I am working on a heavily mathematically project about plasma. In particular, I want to find references that treat the problem from microscopic models that include relativistic and magnetic effects (...
The N's user avatar
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1 vote
2 answers
143 views

Question about the Boltzmann Distribution for an ideal gas

The general statement of the Boltzmann distribution law is that for a system of $N$ particles, each having access to energy states $\varepsilon_1,\varepsilon_2,\dots,\varepsilon_k$, the ratio the ...
Neel's user avatar
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Does collisions of ideal gas molecules effect its equation of state?

I have been reading Statistical Mechanics by R. K. Pathria & Paul D. Beale , 4th edition . In this book they used a quantity called Virial , which is defined as $\mathcal{V} = \langle\Sigma q_iF_i\...
black photon's user avatar
3 votes
1 answer
115 views

A question on relaxation time approximation

I was learned that the form of collision term in relaxation time approximation is set to be: $$\left (\frac{\partial f}{\partial t}\right)_c=-\frac{f-f^0}{\tau}$$ in with $f^0$ is local equilibrium ...
Haiqin Tang's user avatar
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1 answer
97 views

Integration by parts and BBGKY Hierarchy

I'm studying kinetic theory by KineticTheory MichaelmasTerm2012 [1]. Let me bring some context in here. The author have introduce the Lioivelle equation for the distribution $f(q_1,...,q_N,p_1,...,p_N,...
Volodymyr Savin's user avatar
1 vote
0 answers
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Explanation of this proof of distribution of molecules after collision

The below excerpt is taken from Section no.4 from "The Feynman Lectures on Physics Vol.1 Ch.39" (here is the link to the exact text). Here Sir Richard Feynman tries to explain and "...
Bhavya Jain's user avatar

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