A parallel beam of nitrogen molecules moving with velocity v = 400 m/s impinges on a wall

Question:

A parallel beam of nitrogen molecules moving with velocity v = 400 m/s impinges on a wall at an angle θ = 30 ° to its normal. The concentration of molecules in the beam n = 0.9.1019 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.