Question

The atmosphere on a planet is possible only if
[$v_{rms}$ is root mean square speed of gas molecules on planet and $v_e$ is escape speed on its surface]

• A. $v_{rms}=v_e$
  
• B. $v_{rms}>v_e$
  
• C. $v_{rms}\le v_e$
  
• D. $v_{rms}<v_e$
  

Answer 1

The correct option is D $v_{rms}<v_e$


The atmosphere on a planet is possible only if $v_{rms}<v_e$
if $v_{rms}\ge v_{escape}$ the gas molecule will leave the surroundings of the planet. i.e, will be free from gravitational pull of the planet.