Dust Particles Are Pulverized Rock,which Has Density 2500kg/m3

Multiple Choice

Dust particles are pulverized rock,which has density 2500kg/m3.They are approximately spheres with 10μm in diameter.Treating dust as an ideal gas,what is the rms speed of a dust particle at 400°C?

A) 5.2 × 10^-5 m/s
B) 1.7 × 10^-5 m/s
C) 3.0 × 10^-5 m/s
D) 7.3 × 10^-5 m/s