Pressure exerted by a gas (derivation using the kinetic theory of gases)

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Discussion Overview

The discussion revolves around the derivation of pressure exerted by a gas using the kinetic theory of gases. Participants are exploring the relationship between the time between collisions of gas particles with the wall and the change in momentum, as well as the calculation of average force exerted by the gas molecules.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about why the time between two collisions is used for calculating the rate of change of momentum when a particle bounces off the wall.
  • Another participant suggests that the duration of the collision with the wall is the relevant time for the momentum change, questioning the initial claim.
  • A later reply reiterates the need for a reference to support the claims made about the time duration and momentum change.
  • One participant mentions a specific formula for calculating the time taken for a particle to travel to the wall and back, indicating a mathematical approach to the problem.
  • Another participant points out that the average force exerted by gas molecules can be calculated by averaging the change in momentum from the particles colliding with the wall.
  • There are repeated assertions about the need to find the average force over a time period, contrasting it with the instantaneous force which would require a different approach.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the interpretation of the time duration relevant to momentum change and the calculation of force. There is no consensus on the correct approach or understanding of the derivation.

Contextual Notes

Some participants reference specific formulas and concepts without providing full context or derivations, leading to potential gaps in understanding. The discussion also includes informal exchanges unrelated to the technical content.

Who May Find This Useful

Individuals interested in the kinetic theory of gases, pressure calculations, and the mathematical derivation of physical concepts may find this discussion relevant.

Bheshaj
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In the derivation of finding pressure exerted by a gas using kinetic theory of gases I am not understanding why the time between two collisions is taken as the time for rate of change of momentum when a particle bounces back from the wall. please help me
 
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I think you misquote. Any reference ? The duration of the collision with the wall is the time in which the momentum changes.
 
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BvU said:
I think you misquote. Any reference ? The duration of the collision with the wall is the time in which the momentum changes.
BvU said:
I think you misquote. Any reference ? The duration of the collision with the wall is the time in which the momentum changes.
see this
 

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Something gave in in my neck when I tried to read this. Have to go to the hospital first ...

So where is this quote ? I see ##\Delta t = {2L\over |u|} ## for the time to go to the left wall and back again ...
 

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Here in the lower left corner its given that force is change in momentum upon time. where he writes the change in momentum and divides it by time between two collisions as given above it.
 

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They don't have a microscope here in the hospital to read your fine print. Can you be bothered to learn some ##\LaTeX## in order to post legibly ?
 
Last edited:
But if I have to guess he now averages the change in momentum from the gas particles that bump into the wall, to calculate the average force on the wall.
 
Its because yoy want to find average force exerted by the molecule. How u find average force? See u find the time in which this repears aka time period. The collision with wall PQRS repeats. Now find the average force in this time. If u were to find instantaneous force u have to divide by time of collision which is very small.

You are giving Maharashtra HSC? I am also giving it.
 
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Mohammed Ayaz Quadri said:
Its because yoy want to find average force exerted by the molecule. How u find average force? See u find the time in which this repears aka time period. The collision with wall PQRS repeats. Now find the average force in this time. If u were to find instantaneous force u have to divide by time of collision which is very small.

You are giving Maharashtra HSC? I am also giving it.
yeah, me too thanks
 
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BvU said:
But if I have to guess he now averages the change in momentum from the gas particles that bump into the wall, to calculate the average force on the wall.
thanks
 

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