Lecture18

Physics 101: Lecture 18 Fluids II Exam III Textbook Sections 9.6 – 9.8

Archimedes’ Principle ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Archimedes Example ,[object Object], F = m a F b – Mg – mg = 0  g V disp = (M+m) g V disp = (M+m) /  h A = (M+m) /  h = (M + m)/ (  A) = (51.2+9)/(1 x 4 x 4) = 3.76 cm M =  plastic V cube = 4x4x4x0.8 = 51.2 g h mg F b Mg

Review Static Fluids ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Archimedes’ Principle ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],Preflight 1 B =  W g Vol displaced W =  ice g Vol ice   W g Vol melted_ice CORRECT

Preflight 2 ,[object Object],[object Object],[object Object],[object Object],Weight of ship = Buoyant force = Weight of displaced water Tub of water Tub of water + ship Overflowed water CORRECT

Continuity of Fluid Flow ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Faucet Preflight ,[object Object],[object Object],As the water flows down, gravity makes the velocity of the water go faster so the area of the water decreases. Because it scared of the dirty dishes in the sink. wow it does! My faucet does not act this way After the demo involving the bicycle tire and angular momentum, I have decided that physics is sorcery and therefore unexplainable. Ask Harry Potter A 1 A 2 V 1 V 2

Fluid Flow Concepts ,[object Object],[object Object],[object Object],[object Object],[object Object],A 1 P 1 A 2 P 2 v 1 v 2 

Pressure, Flow and Work ,[object Object],[object Object],[object Object],[object Object],[object Object],Demo Recall: W=F d = PA d = P Vol

Pressure ACT ,[object Object],[object Object],There is air pushing on both sides of plates. If we get rid of the air in the middle, then just have air on the outside pushing them together.

Bernoulli’s Eqs. And Work ,[object Object],[object Object],[object Object],[object Object],[object Object],Note: W=F d = PA d = P V

Bernoulli ACT ,[object Object],A B C P 1 +  gy 1 + ½  v 1 2 = P 2 +  gy 2 + ½  v 2 2 Note: All three holes have same pressure P=1 Atmosphere  gy 1 + ½  v 1 2 =  gy 2 + ½  v 2 2 gy 1 + ½ v 1 2 = gy 2 + ½v 2 2 Smaller y gives larger v. Hole C is fastest

Act ,[object Object],[object Object],[object Object],[object Object],[object Object],Note, the correct height, is where the water reaches the atmosphere, so both are exiting at the same height! CORRECT

Example (like HW) ,[object Object],[object Object],[object Object],[object Object],[object Object],Continuity Equation A 1 v 1 = A 2 v 2 v 2 = v 1 ( A 1 /A 2 ) = v 1 ( π r 1 2 / π r 2 2 ) = 2 m/s x 16 = 32 m/s

Lift a House ,[object Object],P 1 +  gy 1 + ½  v 1 2 = P 2 +  gy 2 + ½  v 2 2 P 1 – P 2 = ½  (v 2 2 – v 1 2 ) = ½  (v 2 2 – v 1 2 ) = ½ (1.29) (30 2 ) N / m 2 = 581 N/ m 2 F = P A = 581 N/ m 2 (15 m)(15 m) = 131,000 N = 29,000 pounds! (note roof weighs 15,000 lbs) 48

Fluid Flow Summary ,[object Object],[object Object],[object Object],[object Object],50 A 1 P 1 A 2 P 2 v 1 v 2 

Lecture18

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Lecture18

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