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Applications of Bernoulli’s Principle. Demo’s: Ping Pong Ball in funnel Ping Pong Ball in air stream Paper parallel paper http://www.physics.ucla.edu/demoweb/demomanual/matter_and_thermodynamics/fluids/bernouli_demos.html Note: With demos 1.5 periods. slower speed. faster speed.
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Demo’s:Ping Pong Ball in funnelPing Pong Ball in air streamPaperparallel paper http://www.physics.ucla.edu/demoweb/demomanual/matter_and_thermodynamics/fluids/bernouli_demos.htmlNote: With demos 1.5 periods
slower speed faster speed more pressure less pressure
As the speed of a fluid increases, the pressure in the fluid decreases. P α 1/v
As the speed of a fluid increases, the pressure in the fluid decreases. P α 1/v
Bernoulli & Flight • Bernoulli’s Principle is what allows birds and planes to fly. • The secret behind flight is ‘under the wings.’
AIRFOIL On top: greater air speed and less air pressure On bottom: less air speed and more air pressure
v2 v1 Net force on wing?
LIFT THRUST DRAG GRAVITY
Spoiler – airfoil reversed less air speed more pressure greater air speed less pressure net force: downward
Racecar Spoiler provides better traction and avoids lift
Wind over a roof Patm = Proof + ½ ρv2 v proof v = 0 patm
slow air speed fast air speed
Review Ping pong balls? Cardboard walls? Paper? Baseball?
Instability in passing – Trailers? Trains passing each other?
Atomizer – As air passes at top of tube, the pressure decreases and fluid is drawn up the tube.
2009 Darwin Award (15 December 2009, Germany) A U2 subway driver found a body laying besides the underground tracks in Berlin. Because there was no video surveillance camera at that location, it took police two days to reconstruct what had happened. Apparently Yasin A., 22, was alone in the subway car when he decided it would be a brilliant idea to destroy one of the windows. By swinging feet forward from a handrail into the window, he not only managed to burst the glass but also succeeded in being sucked out of the moving train, and was left dead on the tracks. He was alone in the compartment at the time; if an observer had been present, perhaps the young underground rider would not have engaged in destructive nonsense that led to his senseless death.