Show that 1/2mv^2 = 3/2kT for a star cluster

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Homework Help Overview

The problem involves demonstrating a relationship between the kinetic energy of stars in a cluster and temperature, specifically showing that \( \frac{1}{2}mv^2 = \frac{3}{2}kT \). The context is a stellar system where stars are assumed to have equal mass and are analyzed in terms of their velocities relative to the center-of-mass.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the kinetic energy of stars and its relation to temperature, with some suggesting that stars can be treated similarly to particles in a gas. Questions arise about the assumptions needed to justify this analogy and the specific requirements of the problem.

Discussion Status

There is an ongoing exploration of the problem, with participants sharing their interpretations and questioning the assumptions about the behavior of stars in a cluster. Some guidance is offered regarding the need to justify the analogy to gas particles, but no consensus has been reached on how to proceed.

Contextual Notes

Participants note that the problem requires a demonstration for a cluster of stars rather than individual particles, which raises questions about the underlying assumptions and the nature of the system being analyzed.

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Homework Statement



Demonstrate that the temperature applicable to a stellar system
is
T = m < v2 (x) >
...3k
where it is assumed that the stars have equal mass m, v(x) is the
velocity of a star relative to the center-of-mass, and <> represents
an average.

Homework Equations





The Attempt at a Solution



I don't know how to approach this problem. The only thing I could guess is that the spherically symmetric stars can be considered the particles of a system, so it's just a much larger system, but the physics is the same overall.
 
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Isn't it something like: Assume the stars move about with a mean thermal energy, which is their KE. So KE = 1/2mv^2 = (3/2)KT
Then mv^2 = 3kT => T = mv^2/3k?
 
Physics Enemy said:
Isn't it something like: Assume the stars move about with a mean thermal energy, which is their KE. So KE = 1/2mv^2 = (3/2)KT
Then mv^2 = 3kT => T = mv^2/3k?

I emailed him about it, citing this argument, and he said that we have to demonstrate it for a cluster of stars, not particles.
 
warfreak131 said:
I emailed him about it, citing this argument, and he said that we have to demonstrate it for a cluster of stars, not particles.
But isn't the idea that they are behaving like particles in a gas?
 
Physics Enemy said:
But isn't the idea that they are behaving like particles in a gas?

tell that to him, not me :P

i don't know what the hell he wants us to do
 
warfreak131 said:
tell that to him, not me :P

i don't know what the hell he wants us to do
I think he wants you to justify why they behave like particles in a gas, before you write down the equations. Perhaps Wiki it? I think you need to explain the assumptions.

Hey, would you mind checking my thread? It's a basic numeracy one lol.
 
thats what i was thinking, but then again, you don't know my teacher, or how horrible he is.

and i checked your numeracy question, and I am not quite sure what its asking for :P sorry

i don't want to hijack my own thread and turn it into another question, so i won't discuss it here
 

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