Question

Calculate the rms speed of smoke particles of mass `5 xx 10^(-17) kg` in their Brownian motion in air at NTP. Given `k_(B) = 1.38 xx 10^(-23) J//K`

Answer 1

Correct Answer - `1.5 cm//s`
`C_(rms) = ? M = 5 xx 10^(-17) kg`
`k_(B) = 1.38 xx 10^(-23) J//K T = 273 K`
`C_(rms)sqrt((3kT)/(m)) = sqrt((3 xx 1.38 xx 10^(-23) xx 273)/(5 xx 10^(-17)))`
`C_(rms) = sqrt((4.14 xx 273)/(5)) xx 10^(-2)m//s = 1.5 cm//s`