Finding values of constant by using Dimensional Analysis

In summary, the speed v of sound in a gas can be expressed as v = kpaPb, where k, a, and b are constants. By using dimensional analysis, it can be determined that a = 2/3 and b = 1/3. Therefore, the equation can be simplified to v = kp(2/3)P(1/3).
  • #1
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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  • #2
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.
 

FAQ: Finding values of constant by using Dimensional Analysis

How does dimensional analysis help in finding values of constants?

Dimensional analysis is a mathematical technique used to convert between different units of measurement. It helps in finding values of constants by using the principle of dimensional homogeneity, which states that a physical equation must have consistent units on both sides. By analyzing the dimensions of known quantities in an equation, we can determine the dimensions of the unknown constant and solve for its value.

What are the basic steps involved in using dimensional analysis to find values of constants?

The first step is to identify the relevant quantities and their units in the given equation. Then, we need to determine the dimensions of each quantity and rearrange the equation to express the unknown constant in terms of these dimensions. Finally, we can solve for the value of the constant by substituting in the appropriate units.

Can dimensional analysis be used for all types of equations?

No, dimensional analysis can only be used for equations that involve physical quantities with well-defined units. It cannot be applied to equations that involve abstract concepts or non-physical quantities.

What are some common applications of dimensional analysis in scientific research?

Dimensional analysis is commonly used in physics, chemistry, and engineering to validate equations, convert between units, and derive new relationships between physical quantities. It is also useful in experimental design and error analysis, as it can help identify and correct for any inconsistencies in measurement units.

Are there any limitations or drawbacks to using dimensional analysis to find values of constants?

One limitation of dimensional analysis is that it assumes the equation is dimensionally homogeneous, which may not always be the case. Additionally, it cannot account for the effects of significant figures or experimental errors in the measured values of the quantities involved. It is important to use dimensional analysis in conjunction with other methods of analysis to ensure accurate results.

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