Atmosphere

#1. When considering air: 1- Air has mass 2- Air is not compressible 3-Air is able to flow or change its shape when subject to even small pressures 4-The viscosity of air is very high 5-Moving air has kinetic energy. The correct combination of all true statements is:

#2. Why do the lower the layers contain the greater proportion of the whole mass of the atmosphere:

#3. With increasing altitude, up to about 40,000 ft, the characteristics of air change: 1 - Temperature decreases continuously with altitude 2 - Pressure falls steadily to an altitude of about 36,000 ft, where it then remains constant 3 - Density decreases steadily with increasing altitude 4 - Pressure falls steadily with increasing altitude The combination of true statements is: