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 Bernoulli equation for flowing fluid Pressure changes drive velocity changes and compensate gravity to maintain flow 01 14 2019 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 Hydrostatic pressure Bernoulli equation 01 14 2019 1 2 p v gh constant 2 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 C large ball of gold 01 14 2019 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 01 14 2019 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 01 14 2019 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 01 14 2019 World s first vacuum pump Physics 231 Spring 2011 9 01 14 2019 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 COL LAPSE html Bring the crushed can to class before April 25 Provide an estimate of the force that crushed the can in Newton Extra credit 4 added to quiz score worth 1 missed lecture 01 14 2019 Physics 231 Spring 2011 11 Example for pressure meter 01 14 2019 Physics 231 Spring 2011 12 Clicker Quiz Which force meter shows the largest pressure B E A C D E 01 14 2019 Physics 231 Spring 2011 13 Clicker Quiz Which force meter shows the largest pressure B same 01 14 2019 A Physics 231 Spring 2011 14 Clicker Quiz Which force meter shows the largest pressure same 01 14 2019 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 01 14 2019 Physics 231 Spring 2011 17 Clicker Quiz As object is immersed deeper The volume of displaced fluid A Decreases B Stays the same C Increases NOTE because of string B and C are correct 01 14 2019 Physics 231 Spring 2011 18 Clicker Quiz What will happen to force meter apparent weight when object begins to be immersed in fluid A Force displayed by scale decreases B Force displayed by scale stays the same C Force displayed by scale increases 01 14 2019 Physics 231 Spring 2011 19 Clicker Quiz Once object is fully immersed what will happen to force meter apparent weight when object is immersed deeper A Force displayed by scale decreases B Force displayed by scale stays the same C Force displayed by scale increases 01 14 2019 Physics 231 Spring 2011 20 Clicker quiz Blocks A B have same size How do buoyancies compare B A A A has larger buoyancy B they have the same buoyancy C B has larger buoyancy Reason A displaces more volume and has therefore larger buoyancy force 01 14 2019 Physics 231 Spring 2011 21 Quiz Blocks have different mass with 1 being the lightest and 5 the heaviest All of them are released in the middle of the pool Final locations of 2 and 5 are given Sketch the final locations of 1 3 4 2 1 3 4 5 01 14 2019 Physics 231 Spring 2011 22 Quiz Solution 3 could stay where it is if accidentally its density equals that of water exactly 2 1 3 01 14 2019 4 Physics 231 Spring 2011 5 23 Clicker Quiz A princess sits in a boat on a pond She throws a wooden ball into the water which floats next to the boat Water level in the pond A rises B stays the same C decreases 01 14 2019 Physics 231 Spring 2011 24 Clicker Quiz A princess sits in a boat on a pond She throws a golden ball into the water which sinks to the bottom Water level A rises B stays the same C decreases 01 14 2019 Physics 231 Spring 2011 Reason a floating golden ball in the boat displaces more volume its weight worth of water than a sinking one its volume 25 Laminar Flow http www youtube com watch v blJwTcD1WoU 01 14 2019 Physics 231 Spring 2011 26 Clicker Question B A Where is the flow speed larger A B C speed stays the same 01 14 2019 Physics 231 Spring 2011 27 Clicker Question B A Where is the pressure larger A B C pressure stays the same Explanation water accelerates from A to B the pressure adjust to create the necessary net force to the right with high pressure at A and low pressure at B 01 14 2019 Physics 231 Spring 2011 28
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