Lecture25 - Buoyants force 1) FBuoy-up 1) FLOAT fluid >...

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F Buoy-up mg Buoyant’s force ρ fluid > ρ object FLOAT ρ fluid < ρ object SINK ρ fluid = ρ object Neutral 1) 2) 3) 1) 2) 3) Surface tension Does this means that ? NO ρ insect < ρ fluid Consider a needle or a razor. In water they float…but ρ steel, Al = 7.8 x 10 3 Kg/m 3 ρ H2O = 1 x 10 3 Kg/m 3 ρ H2O < ρ steel Sink! Is the buoyant’s law wrong? gV block ( ρ fluid ρ block ) = ma F Buoy-up – mg = ma
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Think about a trampoline: F restoring The stretched surface layer exerts a restoring force F rest. F s F s, y F s, x Surface tension γ = force/ length = F/L γ is an intrinsic property of fluid ( γ H20 > γ alcohool ) * Note: In a wire tension is a force . In a fluid is a force/length Similarly for the razor, it stretches the surface Restoring force mg F R F R L L h Does not depend on h 2F sy = mg At equilibrium
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Fluid dynamics VISCOSITY Resistance to flow (same as friction) high viscosity = slow flow (e.g. water less viscous than syrup) Turbulent flow: High velocity relative
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This note was uploaded on 10/28/2009 for the course PHYSICS 7A/7B taught by Professor All during the Fall '08 term at University of California, Berkeley.

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Lecture25 - Buoyants force 1) FBuoy-up 1) FLOAT fluid >...

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