The rms speed of particles of mass 5 x 10-17 kg in their random motion in air at NTP will be (Boltzmann’s constant, K = 1.38x10-23 J/K)

given mass of particles=m=5X10−17 Kg, boltzmann constant K=1.38×10−23J/K;Temperature=273kelvin Vrms=3KTm  ; substitute above values, Vrms=(3)(1.38)10−23(273)5X10−17≃15 X 10−3m/s