# lec23 - Physics 140 Fall 2007 lecture #23: 27 Nov Ch 14...

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Physics 140 – Fall 2007 lecture #23: 27 Nov Midterm exam #3 is this Thursday, 29 November – covers chapters 9-12 (rotation through gravity) * stress and strain included * – bring three 3x5 notecards, calculator, #2 pencils Ch 14 topics: mass density hydrostatic pressure Pascal’s principle and (hydraulics) Archimedes principle (floating) A small, continuous piece of a substance (solid, liquid or gas) of mass ! M occupies a volume ! V. Its mass density " is given by the quotient " = ! M / ! V . A dimensionless measure of density, the specific gravity , is the ratio of the density of an object or substance (labeled X) with respect to water " X / " water . mass density

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Collisions of particles (molecules or atoms) within a gas or liquid generate a force against a surface that is in contact with it. Fun Facts about air molecules: (77% nitrogen, 21% oxygen, 1-2%water, 1% other) - typical speed v = 450m/s (1000 mi/hr!) - travel 8x10 –8 m between collisions with another molecule - 6 billion collisions per second on each square inch of your skin pressure Imagine a very small, evacuated plug (b) placed into a container with air or liquid (a). Particles colliding with the outside of the plug
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## This note was uploaded on 04/03/2008 for the course PHYSICS 140 taught by Professor Evrard during the Fall '07 term at University of Michigan.

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lec23 - Physics 140 Fall 2007 lecture #23: 27 Nov Ch 14...

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