Problem 2.65

A parallel beam of nitrogen molecules moving with velocity $v=400 \mathrm{~m} / \mathrm{s}$ impinges on a wall at an angle $\theta=30^{\circ}$ to its normal. The concentration of molecules in the beam $n=0.9 \cdot 10^{19} \mathrm{~cm}^{-3}$. Find the pressure exerted by the beam on the wall assuming the molecules to scatter in accordance with the perfectly elastic collision law.