The mass of a hydrogen molecule is 3.32 * 10-27 kg. 1023 such molecules hit every second on a rigid wall of area 2 cm2 at an angle of 45° with a horizontal velocity of 103 m/s. If the molecules are reflected with the same velocity, then what is the pressure exerted on the wall?
2.35 * 1036
2.35 * 10-13
2.35 * 103
2.35 * 106

Suppose the molecules are incident along PO and reflected along OQ.
Here, < PON = < NOQ = 45°
Change of momentum normal to the wall for each hydrogen molecule = 2mv cos 45°
Net change of momentum in a second = Exerted force = n * 2mv cos 45°
The pressure exerted on the wall