Lecture 02 - Buoyancy. Fluid dynamics

Lecture 02 - Buoyancy. Fluid dynamics - Vacuum gun Sealed...

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1 Lecture 2 Buoyancy Buoyancy. Fluid dynamics. Vacuum gun Sealed tube, air pumped out Ping-pong ball What happens if we punch a little hole on one side? DEMO: Vacuum gun = 2 atm 2 atm 2 1 ~ 2 2 ~ ~ 300 km/s (speed of sound!!!) p FL L mv R vL mR Length of tube ~ 3 m Mass of ball m ~ 3 g Radius of tube R ~ 2 cm ACT: Side tube A sort of barometer is set up with a tube that has a side tube with a tight fitting stopper. What happens when the stopper is removed? vacuum A. Water spurts out of the side tube. stopper B. Air flows in through the side tube. C. Nothing, the system was in equilibrium and remains in equilibrium. DEMO: Side tube DoPaA1 Buoyancy and the Archimedes’ principle y bottom top h A A box of base A and height is submerged in a liquid of density ρ . Σ =− top bottom FF F top Net force by liquid : bottom top Ap ( ) ( ) atm bottom atm top gy ρρ =+ −+ = Ahg Archimedes’s principle: The liquid exerts a net force upward called buoyant force whose magnitude is equal to the weight of the displaced liquid. = direction up Vg bottom
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Slide 3 DoPaA1 Hydraulic puzzle M-HS 8 Department of Physics and Astronomy, 8/24/2010
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2 In-class example: Hollow sphere A hollow sphere of iron ( ρ Fe = 7800 kg/m 3 ) has a mass of 5 kg. What is the maximum diameter necessary for this sphere to be completely submerged in water? ( water = 1000 kg/m 3 ) A. It will always be submerged. B. 0.11 m F B C. 0.21 m D. 0.42 m E. It will always only float. mg The sphere sinks if B Fmg ρπ 3 water 4 3 Rg mg πρ ≤= 3 water 3 0.106 m 4 m R == max Maximum diameter 2 0.21 m Density rule A hollow sphere of iron ( Fe = 7800 kg/m 3 ) has a mass of 5 kg. What is the
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This note was uploaded on 09/21/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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Lecture 02 - Buoyancy. Fluid dynamics - Vacuum gun Sealed...

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