The temperature of an ideal gas is increased from 120K to 480K.The rms Velocity of the gas molecules is v at 120K.At 480k ,it becomes
4v
6v
8v
2v
Since we know that Vrms=3RTMwWe have, Vrms∝T. ⇒(Vrms)T2=(Vrms)T1T2T1Hence VrmsT2=v×480120=2v