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ATMOSPHERE
Lesson 2 - Page 3

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Gravity, including centripetal force of a spinning sphere, pulls on air molecules to stay on the surface. As the Earth spins, the gas molecules response by staying close to the ground. Imagine you are at the amusement park and you enter into a ride. It is circular and they strap you in a cell. The ride begins by spinning and spinning, then the floor starts to fall. You feel like you will fall with the floor, but you donít. You are still "stuck" to the sides by centripetal force.

Movement of the air molecules is also caused by the density of each of the gases. For example, helium is lighter than oxygen so it tends to "escape" into the upper reaches of the atmosphere. Movement of air is dependant on temperature, rotation, and density. Air pressure also changes with height of the atmosphere. The interplay of air pressure can create "fun" activities. Once you do the following demonstrations in lab, you can create similar experiments to amaze your friends.


Centripetal force prevents you from falling


Vertical distribution of wind in a hurricane

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