PSYCH 3A03 Lecture Notes - Restoring Force, Sound Energy, Potential Energy
5 Nov 2013
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Document Summary
Atoms and molecules make up layers in the atmosphere. Despite their size, they exert some weight on us. Air pressure is the weight of air surrounding an object. The weight of air is directly related to the number of air molecules. Air pressure depends on the number of molecules in a given area (space) and how fast these molecules are moving. Density decreases with altitude due to gravity. Net movement is approximately 0 unless there is force. 400 billion molecules per in3 or 1. 21kg per m3. Molecules are moving randomly at about 1500km/hr due to thermal (brownian) motion. More or less evenly distributed and moving equally in all directions (average molecular velocity = 0m/s) Air molecules exert a force (atmospheric pressure) on other objects (e. g. tympanic membrane or ear drum) Air velocity threshold of hearing = 5x10-8m/s. Thus, any systematic (repeatable) oscillations in air pressure (velocity) may be audible. Mass (m) = amount of matter present (kg, lbs)
