Lecture18

Lecture18 - PHYSICS 220 Lecture 18 Fluids Textbook Sections...

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Lecture 18 Purdue University, Physics 220 1 Lecture 18 Fluids Textbook Sections 9.5 - 9.8 PHYSICS 220

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Lecture 18 Purdue University, Physics 220 2 Overview Last Lecture – Pressure is force exerted by molecules “bouncing” off container • P = F/A – Pascal’s Principle • A change in pressure at any point in a confined fluid is transmitted everywhere in the fluid – Pressure in fluid • P = P 0 + ρ gd – Archimedes’ Principle: Buoyant force is “weight” of displaced fluid • F = ρ g V Today – More on Archimedes’ Principle – Moving Fluid – Bernoulli's Principle
Lecture 18 Purdue University, Physics 220 3 Archimedes’ Principle • Buoyant Force F B – Weight of fluid displaced – F B = ρ fluid V disp g – F g = mg = ρ object V object g – Object sinks if ρ object > ρ fluid – Object floats if ρ object < ρ fluid • If object floats… – F B = F g – Therefore ρ fluid V disp g = ρ object V object g – Therefore V disp / V object = ρ object / ρ fluid

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Lecture 18 Purdue University, Physics 220 4 Suppose you float a large ice-cube in a glass of water, and that after you place the ice in the glass the level of the water is at the very brim. When the ice melts, the level of the water in the glass will: A) Go up, causing the water to spill out of the glass B) Go down C) Stay the same CORRECT Exercise W ice = F B = ρ W g V displaced W water = ρ W g V water W ice = W water V displaced = V water
Lecture 18 Purdue University, Physics 220 5 Exercise Which weighs more: A) A large bathtub filled to the brim with water B) A large bathtub filled to the brim with water with a battle-ship floating in it C) They will weigh the same Tub of water Tub of water + ship Overflowed water CORRECT Weight of ship = Buoyant force = Weight of displaced water

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Lecture 18 Purdue University, Physics 220
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This note was uploaded on 09/17/2010 for the course PHYS 220 taught by Professor Chang during the Spring '09 term at Purdue.

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Lecture18 - PHYSICS 220 Lecture 18 Fluids Textbook Sections...

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