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EEJ MAIN Physics QUESTION #7019
Question 1
Calculate the ratio of the root mean square ($rms$) velocities of Helium and Argon atoms, given that the atomic mass of Helium is $4\text{ u}$ and Argon is $40\text{ u}$, both at the same temperature.
  • $3.16$✔️
  • $0.32$
  • $0.45$
  • $2.24$
Correct Answer Explanation
The $rms$ velocity is given by $v_{rms} = \sqrt{\frac{3RT}{M}}$. Since $T$ is constant, the ratio is inversely proportional to the square root of the molar masses: $\frac{v_{He}}{v_{Ar}} = \sqrt{\frac{M_{Ar}}{M_{He}}} = \sqrt{\frac{40}{4}} = \sqrt{10} \approx 3.16$.