At what absolute temperature T is the root mean square speed of a hydrogen molecule equal to its escape velocity from the surface of the moon? The radius of moon is R, g is the acceleration due to gravity on moon's surface, m is the mass of a hydrogen molecule and k is the Boltzmann constant
2mgR3k
The root mean square speed is given by
vrms=√3kTm
The escape velocity is given by ve=√2gR
For vrms=ve we require
√3kTm=√2gR or T=2mgR3k, which is choice (d).