# Questions tagged [dimensional-analysis]

Dimensional analysis means to obtain results by analyzing the units in question, etc. DO NOT USE THIS TAG if your question is about degrees of freedom or spatial dimensions.

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### What does Planck's Length signify about the reality? How do we know that such a length exists? What is the history of its development?

Wikipedia Says - In 1899 Max Planck suggested that there existed some fundamental natural units for length, mass, time and energy.[5][6] These he derived using dimensional analysis, using only the ...
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### Finding equation through dimensional analysis

I am dealing with a homework problem related to dimensional analysis. Earlier on in the problem, I showed that scaling the variables can simplify the problem, and we are now looking at the problem ...
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### Reynolds number in a wind tunnel

I would like to understand how to calculate the Reynolds number in the test chamber of a wind tunnel. It is known that the Reynolds number for a pipe is: $$Re = \frac{UL}{\nu}$$ where $U$ is the ...
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### Undoing problems caused by setting $c = 1$ { or “Undoing $c = 1$” }

In the mathematical derivation of equations for physics, and involving wave propagation in particular, the propagation speed at the start of the derivation is often set to one (c = 1). I am working ...
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### Why is the equation $E=mc^2$?

The equation $E=mc^2$ never made any sense to me. c is a constant (speed of light), therefore c squared is also a constant. We're not specifying any units so surely the equation should be reduced to ...
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### Dimensions in the logarithmic form of the Arrhenius equation [duplicate]

The logarithmic form of the Arrhenius equation is: $\displaystyle\ln k=\ln A-\frac{E_a}{RT}$ Here $k$ and $A$ have dimensions whereas $\displaystyle\frac{E_a}{RT}$ is dimensionless. In other words, \$...
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### Units and measurement

I read on the characteristics of units (i) It should be easily understandable. (ii) It should be changed with change in physical factors. (iii) It should not change with place or time. I want ...