I keep getting “Root-mean-square speed” questions wrong in Kinetic Theory of Gases. What's the trap?
using Celsius temperature in the rms-speed formula.
The usual trap: using Celsius temperature in the rms-speed formula. How to avoid it: molecular-speed formulas always need kelvin. Go back to the definition — The rms speed is the square root of the mean of v^2, not the ordinary mean speed. It links the molecular picture to measurable pressure and temperature.
Key point
Root-mean-square speed
Common mistake
using Celsius temperature in the rms-speed formula.
Memory tip
molecular-speed formulas always need kelvin.
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