A parallel beam of particles of mass m moving with velocities v impinges on a wall at an angle θ to its normal. The number of particles per unit volume in the beam is n. If the collision of particles with the wall is elastic, then find the pressure exerted by this beam on the wall.
Number of molecules hitting 1m2 of wall per
Change in momentum of 1 molecule
= m (2v cos θ) =2mv cos θ
∴ Pressure exerted = N ×change of momentum of 1 molecule
= nv cos θ × 2 mv cos θ = 2mnv2 cos2 θ
