Using the information given in Problem and the properties of the standard atmosphere given in Appendix G, estimate the number of molecules per cubic inch at an altitude of 250,000 ft.
Problem:-
The number of molecules crossing a unit area per unit time in one direction is given by
where n is the number of molecules per unit volume and v is the average molecular velocity. As the average molecular velocity is approximately equal to the speed of sound in a perfect gas, estimate the number of molecules crossing a circular hole 10-3 in. in diameter. Assume that the gas is at standard conditions. At standard conditions, there are 4 × 1020 molecules per in.3.