Julius Sumner Miller: Lesson 8 - Adventures with Bernoulli

When a fluid - a gas or a liquid - flows in a conduit - a pipe - of uniform cross-section - the pressure in the pipe is so much and the velocity of flow is so much. If now the fluid encounters a constriction in the pipe - a narrow-ness - TWO REMARKABLE THINGS OCCUR: The velocity is increased The pressure is diminished These remarkable events tell us how an airplane can fly - how a bird can soar -how a chimney has a good draft - how a flag flutters and a thousand other things. We show an array of exciting DEMONSTRATIONS bearing out these matters. A - Two heavy croquet balls hang side by side with a little gap between. When a stream of air is blown between them they are PUSHED TOGETHER by the greater pressure on their outer sides. B - When a stream of air is blown across the top of a "chimney" - a vertical glass tube - the reduction in pressure is felt in the chimney and the atmospheric pressure outside drives the "soot" - the puffed rice -up the chimney. This is the principle of the atomizer. C - When a ball is lodged in a funnel and the air is driven stoutly into the funnel the ball is NOT driven out! This appears quite illogical until we think of Bernoulli's Principle. D - Using a large-scale atomizer tube we blow a stream of air across the top of the spout of a closed tin can. The reduction in pressure is felt in the can. The atmosphere crushes the can! Very very dramatic! E - A ball is supported on a vertical stream of air. We say the air pushes up -the ball pushes down. Now we deliver the stream of air off the vertical. The ball does not fall down! The secret? The ball is given a spin. This gives rise to a diminution in pressure on the UPPER side of the ball where¬upon the atmosphere below holds up the ball! Wonderful! F - This phenomenon is demonstrated with a Toy Car. The Bernoulli Family has had no likeness in all of history. There were over 120 bearing this illustrious name - and all were uncommon men - nearly all geniuses! In their youngest years they showed remarkable intellectual competence in every body of knowledge - .mathematics - science - languages - philosophy medicine. An incredible thing!