PHY 2020 Lecture Notes - Lecture 14: Fusion Power, Turbulence, Shower
Document Summary
The thickness of our atmosphere is determined by two competing factors: the kinetic energy of its molecules, which tends to spread the molecules apart, and gravity, which tends to hold them near earth. But our atmosphere is a happy compromise between energetic molecules that tend to fly away and gravity that holds them back. The exact height of the atmosphere has no real meaning because the air gets progressively thinner and thinner the higher one travels upwards. This is primarily hydrogen, the most plentiful element in the universe. Air is more compressed at sea level than at higher altitudes. Like feathers in a huge pile, what"s at the bottom is more squashed than what"s nearer the top. For example, when the air pressure inside a cylinder like the one shown in. Figure 14. 2 is reduced, there is an upward force on the piston from the air outside.
