Q. If mass of $He$ atom is 4 times that of hydrogen atom then mean velocity of $He$ is
A) 2 times of $H$-mean value
B) 1/2 times of $H$-mean value
C) 4 times of $H$-mean value
D) Same as $H$-mean value
Explanation
(b) $v_{av} \propto \frac{1}{\sqrt{M}} \Rightarrow \frac{v_{He}}{v_{H}} = \sqrt{\frac{M_{H}}{M_{He}}} = \sqrt{\frac{1}{4}} = \frac{1}{2} \Rightarrow v_{He} = \frac{v_{H}}{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.