Question

Which of the following quantities is zero on an average for the molecules of an ideal gas in equilibrium?

Options

• Kinetic energy

• Momentum

• Density

• Speed

Answer 1

Momentum

Explanation:

Average kinetic energy

= `(1/2mv_1^2 + 1/2mv_2^2 + 1/2mv_2^3 + ....)/N`

= `1/2 m/N(v_1^2 + v_2^2 + v_3^2 + ....)` ≠ 0

Average momentum = `mvecv_{av}` = m(0) = 0

Average density = `"Mass"/"Volume" = (nm)/V` ≠ 

Average Speed = `v_{av} = sqrt((8kT)/(pim))` ≠ 0