1. What is the speed of a sound wave in air at 300°K? What is the speed in helium at the same temperature? Can you explain why a person who has inhaled helium speaks with a high-pitched voice (do not try this yourself)?
2. Find the Mach number of an airplane traveling at 2000 f t/s at altitudes of 5000 f t, 10, 000 f t, 20, 000 f t, and 30, 000 f t. Assume a standard atmosphere.