Atmospheric Pressure, Selected Heights
Compared to the standard Atmospheric pressure at sea level, 760 mmHg = 760 torr, the pressure at some heights above the earth are:
Height  Measured pressure  Predicted pressure 
30 km (19 mi)  9.5 torr  25 torr 
60 km (37 mi)  0.21 torr  .8 torr 
90 km (56 mi)  0.0019 torr  .03 torr 
These pressures are considerably below those predicted by the barometric formula, which can be used to calculate variations in barometric pressure with height near the earth. (The predicted pressures above used temperature 300K and pressure 760 mmHg.) Though the pressure decreases rapidly, even at 200 km (124 mi) there is enough residual atmospheric pressure to gradually slow a satellite, limiting its lifetime.

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Gas law concepts
Kinetic theory concepts 