Question

The reason for the absence of atmosphere on moon is that the :

• A. Value of $v_{rms}$ of the molecules of gas is more that the value of escape velocity
• B. Value of $v_{rms}$ of gas is less than escape velocity
• C. Value of $v_{rms}$ is negiligible
• D. None of above

Answer 1

The correct option is A Value of $v_{rms}$ of the molecules of gas is more that the value of escape velocity

The moon has no atmosphere because the escape velocity on the surface of moon is very less than the rms value of molecule. The molecules will escape and moon cannot hold any atmosphere. Also the value of acceleration due to gravity on the surface of moon is very less. The escape velocity is given $V_{es}=\sqrt{\frac{2gM}{R}}$ and it is $2.38km/s$ for moon.

So, Value of$v_{rms}$ of the molecules of gas is more that the value of escape velocity.