Question

A Blowhard Tests of lung capacity show that adults are able to exhale 1.5 liters of air through their mouths in as little as 1.0 second.1) If a person blows air at this rate through a drinking straw with a diameter of 0.74 cm , what is the speed of air in the straw? 2) If the air from the straw in part A is directed horizontally across the upper end of a second straw that is vertical, to what height does water rise in the vertical straw?

Answer 1

d is diameter, A is the area and v is the speed ,

Area*speed is the quantity of air flowing per second.

A v = πd² v/4 = 1.5 liters /second = 0.0015 m^3/s

v = 0.0015*4/(π*0.0074²) =35 m/s

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2

Using Bernoulli equation

ρ v₂²/2 = hdg where ρ is density of air and d is density of water

h = ρ v₂²/ (2dg) = 1.25*34.8769² /(2*1000*9.8) =0.07758 = 0.078 m