From the conditions of the foregoing problem find the number of molecules reaching a unit area of a wall with the velocities in the interval from `v` to `v + dv` per unit time.

Explanation

Simiarly the number of molecules reaching the wall (per unit area of the wall with velocities in the interval `v` to `v + dv` per unit time is
`dv = int_(theta = 0)^(theta = pi//2) dn (v) (d Omega)/(4 pi) v cos 0`
=`int_(theta = 0)^(theta = pi//2) n((m)/(2 pi kT))^(3//2) e^(-mv^2//kT) v^3 dv sin theta cos theta d theta xx 2pi`
=`n pi ((m)/(2 pi kT))^(3//2) e^(-mv^2//2kT) v^3 dv`.