Question

The root means the square speed of smoke particles of mass 5 × 10^-17 kg in their Brownian motion in air at NTP is approximate.

[Given k = 1.38 × 10^-23 JK^-1]

Options

• 60 mm s^-1

• 12 mm s^-1

• 15 mm s^-1

• 36 mm s^-1

Answer 1

15 mm s^-1

Explanation:

The root mean square speed of smoke particles is given by

v_rms = `sqrt((3kT)/m) = sqrt((3 xx 1.38 xx 10^-23 xx 293)/(5 xx 10^-17))` ≈ 15 mm/s