Finding values of constant by using Dimensional Analysis

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SUMMARY

The discussion focuses on determining the constants 'a' and 'b' in the power law equation for the speed of sound in a gas, expressed as v = k * p^a * P^b. Through dimensional analysis, participants established that the left-hand side of the equation, representing speed, has dimensions of [L][T]-1, while the right-hand side combines the dimensions of density and pressure raised to their respective powers. The conclusion reached is that the values of 'a' and 'b' must be -1/2 and 1/2, respectively, allowing for the equation to be simplified to v = k * (P/p)1/2.

PREREQUISITES
  • Understanding of dimensional analysis
  • Familiarity with power law equations
  • Knowledge of physical dimensions (mass, length, time)
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study dimensional analysis techniques in fluid dynamics
  • Explore the implications of power law relationships in physics
  • Learn about the derivation of equations of state for gases
  • Investigate the role of dimensionless constants in physical equations
USEFUL FOR

Students in physics or engineering, educators teaching dimensional analysis, and researchers interested in fluid dynamics and thermodynamics.

Byeongok
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Homework Statement


The speed v of sound in a gas depends on the density p and pressure P of the gass. If this dependence is in the form of a power law that is,

v = kpaPb

where k, a and b are constants (k a dimensionless one).
a. Determine by dimensional analysis the values of a and b.
b. There by rewrite the above equation in a simpler form.

Homework Equations



v = kpaPb

The Attempt at a Solution


[/B]
I started off by writing the dimensions in the equation

[L][T]-1 = ( [M][L]-3 )a ( [M][L]-1[T]-2 )b

From here, i think i have to try and find the values for a and b that allows the right hand side of the equation to match the left. Also in this situation, do i just leave K out of it?
Any help to proceed to next step towards the answer would be great.
 
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Byeongok said:
From here, i think i have to try and find the values for a and b that allows the right hand side of the equation to match the left.
Right.
Byeongok said:
Also in this situation, do i just leave K out of it?
k is dimensionless, so it is irrelevant here.
 

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