Questions tagged [kinetic-theory]

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

Filter by
Sorted by
Tagged with
0
votes
0answers
13 views

Defining “rate” as absolute difference

My understanding of rate a quantity relates to how that quantity changes with time. In this paper I am reviewing, they defined "bearing rate" of any two ...
1
vote
1answer
59 views

How can we take pressure of ideal gas be equal to pressure of atmosphere if container is open

I can better put my doubt in form of problem: The temperature of a gas placed in an open container is raised from $27^o$ C to $227^o$ C. The percent of the original amount of the gas expelled from the ...
0
votes
1answer
31 views

Doubts related to some assumption of kinetic theory

I have doubts related to the kinetic theory of gases which are mostly conceptual which I cannot find in my textbooks. How assumptions the molecules to be perfectly rigid and spherical be good since ...
1
vote
1answer
53 views

Why collisions with other molecules not taken in account here?

I have few doubts related to this derivation why collisions with other molecules not taken into account since they could also influence the time it takes for one molecule to collide with the wall how ...
0
votes
0answers
12 views

Volume correction of Van der Waal's equation

A simple derivation of the ideal gas law by assuming all gas molecules to be perfect spheres is as follows: Considering some area of the wall of a container A, the pressure exerted by all molecules ...
0
votes
2answers
26 views

Why we take time between consecutive collisions on the same wall in derivation of pressure exerted by ideal gas on container by one molecule?

My doubt is why we take time between two consecutive collision $2L/v_{x}$ on the same wall if distance between two parallel face of wall is $L$ instead of the time molecule takes to hit the wall and ...
1
vote
0answers
24 views

Is there a way to solve this question using instantaneous center method? [closed]

This question is about instantaneous center method of finding velocities. I saw this question on a exam paper, but i think the question may be wrong because i couldn't find a way to get IC(1,3) Or ...
0
votes
1answer
26 views

Doubt about why to consider partial pressures in calculating vapour pressure [closed]

I am confused as to why the partial pressure is considered while calculating whether a liquid will evaporate in atmosphere or not. But doesn't the reasoning given of molecules colliding also consider ...
1
vote
0answers
30 views

Confusion with degrees of freedom [closed]

I am facing a lot of confusion regarding the degrees of freedom of various molecules. I want to know some facts with certainty. I will talk about what I have read, please correct me if I am wrong. I ...
0
votes
2answers
40 views

Distribution of molecular speeds (kinetic theory of gases)

What is the physical significance of the $N(v)$? I know that the product $N(v)\ dv$ gives the number of molecules in a given speed range of $v$ to $v+dv$ but is there any meaning of $N(v)$ itself? ...
2
votes
2answers
85 views

What is the theoretical justification for the Law of Equipartition of Energy?

What is the theoretical justification for the Law of Equipartition of Energy? Why are equal energies distributed in each degree of freedom even though sometimes they are completely different (like ...
0
votes
0answers
42 views

Divergence theorem & Kinetic model of plasmas

In one section in my plasma physics notes (see below) on the Vlasov equation, 6D phase space & the kinetic model for plasma, I can't quite understand how (via Gauss's divergence theorem) this ...
4
votes
3answers
242 views

Is it possible for two gases to have different internal energy but equal pressure and temperature?

Apparent contradiction between specific heat ( i.e internal energy, in this case) and average kinetic energy (i.e temp). For ex- if i take two gases [He] and [Xe] then xenon have more specific heat ...
1
vote
0answers
54 views

Good reference for undergraduate introduction to the Master equation and Fokker-Planck equations

So I have a background in statistics and differential equations, but not much physics at all. But I am working on a project relating to stochastic differential equations and Markov processes. I was ...
0
votes
2answers
45 views

How many Degrees of Freedom do Linear Triatomic Gas Molecules Have and Why?

I read this in one of my textbooks that stated Linear Triatomic Gas Molecules like CO2, HCN, CS2 in which all the atoms are linear, the total number of degrees of freedom are Nf = NT + NR + NV where ...
0
votes
1answer
33 views

Thermodynamic function describing an ensemble [closed]

Consider an ensemble of thermodynamic systems each of which is characterized by the same number of particles, pressure and temperature. The thermodynamic function describing the ensemble is (a) ...
0
votes
1answer
40 views

Boltzmann equation: how to estimate the relaxation time?

I am looking for qualitative/general explanations or references. A famous approximation of the full integro-differential Boltzmann equation is the so-called "relaxation time approximation", ...
1
vote
1answer
40 views

Kinetic average energy of $N$ particles [closed]

Really quick doubt: we know that $\overline{E_c}=\frac32 kT$ where $k=1.38\cdot 10^{-23}\frac{J}{K\cdot particles}$ but particles isn't really a unit, I know, but imagine they ask me about $N$ ...
0
votes
0answers
32 views

Deriving Bernoulli's equation with the kinetic gas theory: Missing 1/2 factor

Inspired by Eugene Khutoryansky video about Bernoullis law (https://www.youtube.com/watch?v=TcMgkU3pFBY), I decided to put the thoughts and ideas from her video into mathematical terms. My derivation ...
0
votes
3answers
69 views

In particle physics what is the derivation of the mean free path length: $\ell=\frac{1}{n \sigma}$?

From my lecture notes (ICL, dept. of Physics) it is written: Consider a thin piece of material with thickness $d$ containing target particles with number density $n$, as illustrated in Figure $\bf{2....
0
votes
1answer
41 views

Difference Between Molecular Dynamics and Kinetic Theory? Loschmidt's

Disclaimer : Im not a physicist! I have heard Loschmidt's paradox described as "the laws of thermodynamics are time asymmetric because entropy always increases, but the underlying laws of physics ...
0
votes
1answer
19 views

To define an equation of state, does the system need to be in some type of equilbrium?

Typically one assumes some sort of equilibrium to define an equation of state for a system. However, I am curious if equilibrium is actually required to define a general equation of state (with the ...
1
vote
2answers
32 views

How does heating up a gas affect the average speed of the gas particles?

I think that heating up a gas increases the temperature of the gas. A higher temperature increases the speed of the particles in the gas. However, there is a step missing from my answer to get full ...
0
votes
1answer
66 views

Maxwell-Boltzman Energy Distribution

The Maxwell-Boltzmann probability density function for the energy is $$ f_{MB}\left(E\right)=2\left(\frac{1}{\text{K}_{B}T}\right)^{3/2}\sqrt{\frac{E}{\pi}}\exp\left(-\frac{E}{\text{K}_{B}T}\right) $$ ...
0
votes
2answers
37 views

Orthogonality of two randomly chosen velocity vectors in the kinetic theory of gas and the relative velocity

I was looking for the average value of the relative velocity of ideal gas molecules in the kinetic theory. The following is from this article. The vector notation is not mathematically rigorous, just ...
0
votes
0answers
41 views

How can we derive the kinetic gas equation?

I was reading the kinetic theory of gases and I am confused with the derivation of kinetic gas equation in my book. It started by taking an example of an atom moving along the X axis with a speed $U_x$...
0
votes
0answers
21 views

Coefficient of viscosity from Kinetic Theory of Gas

I have a confusion in the derivation of coefficient of viscosity from the book: 'Concepts in Thermal Physics' by Blundell-Blundell. I am adding highlighted part in which I have confusion (the full ...
1
vote
0answers
32 views

Thermal transport in a rotating fluid

Suppose that we have a rotating fluid with nonzero heat conductivity and the rotation is uniform and stationary. The centrifugal force should then be compensated by the gradient of temperature (assume ...
0
votes
1answer
45 views

If I drop some things from a distance how do I know which one has the deepest or shallower depression? [closed]

Suppose I drop something from 200 cm and another thing from 20 cm. Which will cause a deeper depression?
1
vote
3answers
71 views

Why the collisions of molecules with the wall in kinetic theory are 'elastic'?

I simply don't understand the reason such collisions are elastic. The elastic collision should be satisfying 1. (kinetic) energy conservation and 2. momentum conservation. Lets saying the wall is on $...
2
votes
3answers
58 views

For a gas in an open vessel, should the volume of gas be the volume of whole universe?

In the ideal gas equation $PV=nRT$, $V$ is defined as free space available to the gas. In an open vessel in which temperature is maintained constant, shouldn't the volume $V$ of the gas be the volume ...
0
votes
0answers
17 views

How do we explain No change in Entropy in an Adiabatic Quasi-Static Expansion from the perspective of Boltzman's Idea of Entropy?

I understand from the formula of Clausius idea of Entropy that the change in entropy in an adiabatic quasi-static process is zero. I do not understand, how we can explain the same idea from the ...
1
vote
3answers
105 views

What is the kinetic energy of one molecule of a polyatomic gas?

According to Kinetic theory, the kinetic energy of one molecule of gas is 3/2kT. Is this true for diatomic and polyatomic gases as well? I've read that a diatomic gas has 5 degrees of freedom (3 ...
1
vote
0answers
28 views

A question on mean free path of gases in a container [closed]

Two identical containers kept at the same temperature carry the same gas with different molecular mean free paths l1 and l2. the gas from the first container is completely transferred in to the ...
1
vote
1answer
71 views

Why do we use RMS speed rather than just taking the average of absolute value of the speeds?

I get that negative values to cancel positive values, and that is the reason why we don't do a direct average. So why don't we just use the absolute value mean of the speed? If I have one gas particle ...
2
votes
1answer
26 views

Does the Maxwell Boltzmann velocity distribution deal with the velocity of centre of mass

Very basic question here. Does the Maxwell Boltzmann velocity distribution deal with the speed of the centre of masses of multiatomic( like Nitrogen ,oxygen) species or with the exact speeds of atoms?...
3
votes
2answers
168 views

Why is the temperature of a gas proportional to the average kinetic energy of its particles?

I'm studying the kinetic theory of gases I managed to derive that pressure is inversely proportional to volume and directly proportional to the average kinetic energy of the gas particles. Similarly, ...
0
votes
1answer
28 views

How does one physically achieve a constant state variable process in thermodynamics?

Recently, I was studying about the various different paths which we can go through in thermodynamics, and, I wish to ask how exactly we can achieve a process such as a constant temperature or ...
0
votes
1answer
38 views

What happens to Atom KE when it's supressed by other forces?

Assume fallowing situation: Atom 1 travels in direction of Atom 2 with velocity (kinetic energy) vy. As Atom 1 gets closer to Atom 2, the Atom 2 repealing forces have more impact on Atom 1. At some ...
0
votes
2answers
48 views

Atom kinetic energy transfer

So according to physics laws, energy can't be created or destroyed but transformed from one form to another. But what happens when an atom flows with certain velocity and is stopped by other atom's ...
0
votes
0answers
69 views

Why do atoms move?

According to Kinetic theory of matter: "All matter is made up of atoms and molecules that are constantly moving". But why? What is the deep explanation for the movement (translate, rotation ...
2
votes
5answers
107 views

Maxwell-Boltzmann distribution in conductors?

In the kinetic theory of gases, the Maxwell-Boltzmann distribution is commonly used to describe the velocity distribution of gas molecules. My question is to what extent (if at all) can such a ...
1
vote
3answers
172 views

Looking for an alternate derivation of collision frequency of ideal gas molecules with the container walls

I've learnt how to calculate the collision frequency of ideal gas molecules with the walls of container using Maxwell Boltzmann distribution given as $$ f=\frac{1}{4} n\langle v\rangle$$ However I was ...
0
votes
1answer
45 views

Why $dE + dW = C_pdT$?

$dE$ is Internal Energy $dW$ is Work Done $C_p = $ Specific heat at Constant Pressure In Mayer's Reaction, They have given the relation $dE + dW = C_p.dT$ But I don't know how they have Derived this ...
1
vote
1answer
34 views

Why does thermal conductivity decrease from solids to gases?

I am learning in my heat transfer class that the thermal conductivity decreases from solids to liquids to gases i.e. $$K_{solid} > K_{liquid}>K_{gas}$$ The reason cited is that (based on my ...
1
vote
2answers
81 views

Interpretation of kinetic energy and temperature in thermodynamics

Consider the question above. Till now I have interpreted kinetic energy as a consequence of temperature in thermodynamics, i.e., the kinetic energy of a gas is directly proportional to its temperature....
1
vote
1answer
25 views

Looking for a way to derive the velocity distribution along x axis given the distribution for a general velocity

Without recourse to statistical mechanics my book derives the well known Maxwell Boltzmann velocity distribution which is: $$dN(v)=N\left(\frac{m}{2 \pi k T}\right)^{3 / 2} e^{-m v^{2} / 2 k T} 4 \pi ...
1
vote
2answers
63 views

Kinetic Equation of Gas: Why is $T$ not the time of impact?

so i just learnt about about the derivation of Kinetic Gas Equation! In that derivation, and i have a question which i am trying to find the answer for but i can't find it anywhere on the internet! In ...
0
votes
0answers
63 views

Finding the average speed of a diatomic gas

Question is simple: I was asked to find the average speed of oxygen gas molecules at $T = 300^o K$. I thought the answer was simple too, as simple as plugging in the equation for $v_{avg}$ which is ...
2
votes
2answers
72 views

How to define temperature in non-equilibrium, non-thermodynamic systems?

This question stems from an answer to the following question: What's the most fundamental definition of temperature? The issue here is how to define the temperature in a system not in thermal or ...

1
2 3 4 5
12