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[Music]
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how do you do ladies and gentlemen and
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boys and girls I am juliia Su Miller and
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physics is my business and my business
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today has most uncommon enchantment and
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of all the things I like to do of which
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there are hundreds in this business of
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demonstrations this indeed enchants my
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soul the most it has to do with the
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principle of beri beri b e r n o u l l i
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and I urge you to go and read about the
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bruli because they were an uncommon
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family a 100 20 of them all
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Geniuses unlike anything in the history
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of the humankind the best that we've
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ever had are the Box in music and there
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were only at most 24 of those but can
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you imagine over a hundred people named
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beri all Geniuses not one an ordinary
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man now I will recite to you quickly and
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passingly the principles lying here in
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these
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demonstrations which you can read about
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in your books first we learn from beri
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that when a moving fluid like air
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encounters a constriction that is a
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narrow space the velocity increases so
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as we say the velocity is increased in a
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constriction one other principle emerges
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from a study of beri and that is that
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the pressure in a constriction
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diminishes diminishes or goes down
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so we have these two principles velocity
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increases pressure diminishes in a
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constriction and now I'm going to show
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you an abundance an array of experiments
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demonstrations that reveal this consider
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the following why an airplane can fly
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says Beni he explains why why a ball can
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be thrown in a curve why a chimney has a
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good draft why a bird can
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soar uh why a boomerang uh whatever it
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does boomerangs all of these things can
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be accounted for in terms of beni's
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principle here is a magazine opened so
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that the pages are curved in this way
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and now I am going to blow a stream of
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air against the inner edge of these
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pages one would think that they would be
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pushed down by the push of the air but
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no watch
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watch
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well the page was lifted up there it is
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now that airplane wing has some flutter
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which we don't want of course in the
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real airplane wing but the air going
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over the top gave rise to a diminution
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and pressure and the atmosphere below
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lifted the page up consider another of
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the same here are two spheres two
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croquet balls with a little separation
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between them and this region is a
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constriction I'm going to blow some air
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through there
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one would think impulsively that the
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Spheres will be blown apart no they are
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not the pressure will be reduced and the
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atmosphere will push them together watch
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it there they are pushed together by the
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greater atmospheric pressure on the
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outside now of what consequence is this
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well very important indeed because if
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two ships pass let us say two ships
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passing on the sea if they pass too
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close to one another the pressure is
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reduced between them and they could be
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made to collide and and and break
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apart here is
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another very dramatic my chimney effect
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here I have a chimney you remember a
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requirement of our work together is
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Imagination so I could of course draw
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the picture of my house and my chimney
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and there's the fireplace in my house
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now why does my chimney have a good
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draft it has a good draft if there is a
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stout wind blowing across the top of the
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chimney why because high velocity
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diminution and pressure the atmosphere
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atmospheric pressure pushes the smoke up
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the chimney I'm going to prove that here
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is my fireplace my fireplace is a vessel
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with some puffed rice here is the
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chimney I'm going to blow a sharp stream
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of air across the top the pressure will
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be reduced here in this region the
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reduction and pressure will be felt in
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the tube and the atmosphere will push it
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up watch
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it there it is my chimney has an
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extraordinarily good draft watch it
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there it is I say that's a terrific
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chimney now here's one that's even
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better still here's a funnel and I'm
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going to put some puffed rice in that
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funnel and then I'm going to blow some
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air through that funnel just to show you
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that air is blowing out of that funnel
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watch it now well oh well of course
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there it is sure the puff rice couldn't
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have come out unless I blew it out now
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I'm going to put a pingpong ball in
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there there it is now I'm going to blow
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that pingpong ball
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out watch
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it
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indeed somebody says oh he's got it
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stuck in there by magnets or something
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no no I will dispose of it as quickly as
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I can with the following remark here it
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is here it is here is the
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funnel there is the ball here is the air
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the ball fits in the funnel very snugly
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and these regions right here are
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constrictions and when the air passes in
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there it has a high velocity and a
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reduction in pressure and the atmosphere
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holds the ball
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up indeed this principle of granuli is
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why an atomizer works you know what an
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atomizer is an atomizer is a tube that's
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resides in a vessel and here is some
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liquid and here is a tube across here
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and here is a bulb and you squeeze the
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bulb air rushes across there is a
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reduction in pressure the atmosphere
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pushes the liquid up and then the liquid
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is caught in the airst Stream and comes
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out there I have often thought that the
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reason that's called an atomizer is
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because little atoms of the liquid come
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out there don't you like that idea
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little atoms now here is an
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atomizer and spray would come out there
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now I'm going to show you an atomizer on
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large scale watch it this is
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fantastic here is a tin can and here is
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a tube quite like that one residing in
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the atomizer and I'm going to blow a
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stream of air through this tube there
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will be a reduction of pressure in the
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tin can and now what will the atmosphere
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do
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if the can has less pressure inside the
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atmosphere will collapse it because it
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is enormously strong watch it
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watch there it is there it is I tell you
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that's terrific it's so terrific I'm
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going to do it again with another one
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there's another one yeah why well if I
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like it I'm going to do it twice I may
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do it three four times watch
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it oh look at that well that's two times
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and I'm going to do it once more once
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more why because I like it
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watch oh oh there it is notice notice
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there it is wait there it
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is there it is and I tell you that's
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terrific that's
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fantastic
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now pressure reduced in the
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construction velocity
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increased consider
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a
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consequence
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flag United States flag Australian
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flag why does a flag flutter
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beri have you not heard sometimes your
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Venetian
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blinds chatter beri the air blowing
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across the top of the shutter gives rise
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to a reduction in pressure the shutter
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is lifted up now because of its
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springness and its inertia it falls back
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and so it oscillates and I'll tell you
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how powerful an instrument Bern's
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principal is some years ago a bridge way
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up in Northern Washington collapsed
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because of the effect of berly's
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principle because of the role beri
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played now we got something wonderful
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terrific oh why is it terrific because
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you would not believe it here it is
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suppos and I had a tool Tu and I drove a
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stream of air up here and I had a ball
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right at the top vertically above the
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blowing air you would say if the ball
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stays there it's because the air pushes
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up and the ball pushes down and when
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they are equal the ball stays there and
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that would be correct but now supposing
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I turn the tube off the vertical and the
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ball still stayed there well you can't
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say that anymore because when the ball
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receives the air that way there is a
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component that way and a component that
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way that one may hold up the ball but
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this one should drive it away but I'm
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going to show you that it doesn't watch
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it oh little
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trouble uhoh let me try a heavier ball a
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golf
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ball
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[Music]
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and I call to your attention a very
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significant feature of this the ball was
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spinning this spin gave rise to a
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reduction of pressure on the upper side
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whereupon the atmosphere held it up
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let's take a big one like this
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and I say that's terrific I just love
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that I want to do it again because I
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do any objections
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notwithstanding question could I get
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that ball on the horizontal that's a
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good one to explore indeed you can do
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this by going to your gasoline station
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and using the air holes At Your Service
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Station uh let me do it again with a
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golf ball which is quite heavy golf ball
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quite
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heavy oop little
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trouble now
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finally since I enjoy as you know the
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physics in toys here is a wonderful
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demonstration of beri here is a little
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toy car here is a little toy car and
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what am I doing I am storing some energy
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in a wound up Spring and when I release
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the
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spring it unwinds and turns a fan and
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there is a stream of air emerging from
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here I'm going to show you that there is
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watch it there is a little polystyrene
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ball there it is
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now remember I can put that off the
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vertical watch
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it there it is now what I'm going to do
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should be an enchantment for ages 4 to
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94 as all the physics that we do should
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be watch it now
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watch oh is that
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do look at
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that I want to do that again cuz I like
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it
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there it
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is this is a beri car and why does it
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work as it does because one there is a
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push of the air a high velocity on one
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side of the ball which gives rise to a
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diminution and pressure and
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thereby the atmospheric below holds it
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up
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now what shall we say about bruli the
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applications are phenomenal as I Remar
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two ships passing uh on the sea should
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not pass too close to each other indeed
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have you not stood on the sidewalk when
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a fast moving vehicle has gone by and
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you have been made to rock or have you
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not passed in your car a bus let us say
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and your car is made to rock this is a
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consequence of the reduction in pressure
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between the vehicles where upon the
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atmosphere on the outside pushes them
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together indeed when the Japanese design
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their most recently uh accomplished
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railroad from Osaka to Tokyo where the
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trains go about 120 M an hour what was
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the critical thing several one the
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center of gravity idea number two how
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close can the cars be without the effect
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of beri and so I say read about the beri
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they are wonderful to know about and I
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thank you for your
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attention
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[Music]
