Topic Fluids PHYSICS 231 Key Concepts Density Volume Mass density as material property Pressure units how to measure direction Hydrostatic pressure in liquid on earth Buoyancy and Archimedes Principle How to calculate buoyancy force Floating and sinking Continuity equation for incompressible liquid Sets fluid speed for a given flow along a pipe Bernoulli equation for flowing fluid Pressure changes drive velocity changes and compensate gravity to maintain flow along a pipe 3 18 11 Physics 231 Spring 2011 2 Key Equations Note that these are only useful once you understood the concepts and can derive equations that apply to a specific problem Pressure p F A p p0 gd Buoyancy force upward FB f V f g Continuity Av constant Hydrostatic pressure Bernoulli 3 18 11 1 2 p 2 v gh constant Physics 231 Spring 2011 3 Density Slide 13 12 Clicker quiz These balls are sorted by increasing weight Which has the smallest density A small ball of gold B large ball of aluminum Density depends on material not shape or size C large ball of gold 3 18 11 Physics 231 Spring 2011 5 Clicker quiz These balls are sorted by increasing weight Which has the smallest volume A small ball of gold B large ball of aluminum C large ball of gold 3 18 11 Physics 231 Spring 2011 6 Clicker quiz All objects made of the same material have A The same density regardless of their weight and volume B The same volume regardless of their density and mass C The same mass regardless of their density and volume 3 18 11 Physics 231 Spring 2011 7 Atmospheric Pressure patmos 1 atm 103 000 Pa Slide 13 16 Magdeburg Hemispheres Otto von Guericke 1602 1686 German scientist and mayor of Magdeburg 3 18 11 World s first vacuum pump Physics 231 Spring 2011 9 3 18 11 Physics 231 Spring 2011 10 Extra Credit Project Crush a soda can at home using normal air pressure see for example http scifun chem wisc edu homeexpts COLLAPSE html Bring the crushed can to class before April 25 Provide a written estimate of the force that crushed the can Extra credit 4 added to quiz score worth 1 missed lecture 3 18 11 Physics 231 Spring 2011 11 Example for pressure meter 3 18 11 Physics 231 Spring 2011 12 Clicker Quiz Which force meter shows the largest pressure B A C D E E 3 18 11 Physics 231 Spring 2011 13 Clicker Quiz Which force meter shows the largest pressure B A They show the same 3 18 11 Physics 231 Spring 2011 14 Clicker Quiz Which force meter shows the largest pressure They also show the same 3 18 11 A B C Physics 231 Spring 2011 15 Slide 13 17 Clicker Quiz As object is immersed deeper The volume of displaced fluid A Decreases B Stays the same C Increases 3 18 11 Physics 231 Spring 2011 17 Clicker Quiz As object is immersed deeper The volume of displaced fluid A Decreases B Stays the same correct if neglecting string C Increases correct if considering string NOTE because of string B and C are considered correct 3 18 11 Physics 231 Spring 2011 18 Laminar Flow http www youtube com watch v blJwTcD1WoU 3 18 11 Physics 231 Spring 2011 19
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