The physics of floating screwdrivers----make money online

the YouTube channel Nighthawk and light

recently posted an interesting video

showing how you can float an ordinary

screwdriver on a jet of compressed air

so I've got my compressed air gun here

at about a hundred psi let's see if we

can get this to work a pretty neat trick

and so me being me I wanted to find out

what was going on here so I built a sort

of a screwdriver placeholder this is

just a piece of plastic that I turned on

the lathe with a steel shaft sticking

out same thing and believe me I tried

for many minutes and this doesn't work

so what kind of weird magic flaw is this

only actual screwdrivers are allowed to

float on air but I actually learned some

interesting stuff about fluid dynamics

and I thought I'd share it with you in

this video if you're going to try this

yourself the trick is to hold the

screwdriver away from the handle and

then position the air jet just about

vertically and put the screwdriver over

the air jet just about like this so that

the air jet is pointing right about here

on the screwdriver and you'll feel as

you're blowing air across it that the

screwdriver kind of locks into place and

then you can let go and it will float

there so of course I tried it on other

screwdrivers this one works just fine as

well this one's a bit heavier but when I

tried it on my own homemade sort of

screwdriver it doesn't float and I tried

for many minutes to make this work so

what's going on here this it's almost

exactly the same shape and weight and

weight distribution as the real

screwdriver and I started thinking that

the upper edge here was kind of a

critical part of this whole thing so I

made another fake screwdriver and this

one actually has a rounded top so you

can see one of these is square cut and

the other is rounded and I turned both

of these on the lathe this one floats

just fine and this one doesn't float at

all it falls no matter what you do to it

so what's happening is the air is

rushing out of the nozzle and flowing

around the screwdriver handle and in the

case of the normal shaped screwdriver

handle the air mostly sticks to the

surface of the handle until it gets to a

point on the back edge here where it

suddenly separates and returns to its

straight direction or returns to a flow

that's dominated by the jet and what

that's called a separation because

mainly it's it's flowing along and

sticking to the surface and

getting to the point where the forces

trying to pull it away overcome the

forces that are pulling it down to the

surface and in this region here there's

a low-pressure zone and that's actually

what holds the screwdriver up so we've

got gravity tugging down on the

screwdrivers center of gravity and then

we've got this lift force generated by

the low-pressure zone behind the handle

now in the case of the square handle

there's a lot of turbulence created by

that sharp edge there so as the air

flows around that sharp edge the air

starts you know eddy current and flowing

around and swirling and all kinds of

stuff and that actually disrupts the

area of this low-pressure zone so

instead of having a really nice piece of

vacuum up in here well I mean a

low-pressure area holding the

screwdriver up we've got this swirling

mass of air and so we don't actually get

any lift out of this this is exactly the

same reason that tennis balls and golf

balls have a surface texture to them you

know golf balls have dimples and tennis

balls are fuzzy so when they're moving

through the air that fuzz or dimpled

surface actually creates turbulence and

that overall creates a smaller

low-pressure zone behind the ball if the

balls were smooth then the air would

stick to them very well and you'd

actually get this really good

low-pressure zone behind it which would

slow down the ball or make it travel not

as far so just to make sure that there

aren't some weird physical laws that

only apply to screwdriver shaped objects

I turned a solid section of plastic with

the smooth edge up here and this

actually floats just fine

so that proves that we're really only

interested in this upper edge up here

and the rest of it doesn't really matter

then thinking that I understood this

well enough I turned a cone-shaped

screwdriver look-alike and thinking what

would happen is the air would you know

smoothly flow over the cone and there

would be no way we could have this

low-pressure zone because the cone would

basically be taking up that space and

this one would clearly fall because this

wouldn't generate any low-pressure zone

actually this one floats just fine I was

really surprised but this one's actually

even more stable than all the others so

clearly there's still separation going

on and there's still enough low pressure

to hold this up so then I turned a more

extreme cone

this one falls so I eventually got the

angle the taper is gentle enough here

where in this case the air flows

smoothly down the taper and there's no

spot where we can generate this

low-pressure zone to hold the thing up

and it falls so we have two ways of sort

of making the screwdriver fall we can

either have a sharp edge which causes

turbulence and that disrupts the

low-pressure zone like this or we can

have a really really gradual taper the

air just smoothly flows down there and

there's no way to create this this

low-pressure zone behind it because the

cone is basically taking up that space

to investigate this a little bit further

I built a simple flow demonstrator box

and so I've got an acrylic sort of open

topped box and I put a small aquarium

pump in there with a hose connected to

it and I punched a bunch of small holes

in the hose and then wrapped the hose up

in filter floss so then I have a very

continuous stream of liquid coming down

and the liquid is Reynaud scopic fluid

it's basically very fine glitter in

water and it shows the flow patterns

that the water is experiencing I made a

couple dummy mock-ups of the different

shapes that I tried for floating

screwdrivers and you know be aware that

this is totally not a scientifically

accurate sort of representation of

what's going on in air because we're in

water now and I didn't compensate for

all the differences there but this will

give you a visual indication of what's

going on and you can see that there's

actually a pretty big difference between

having a smooth edged box shape and a

sharp edge box shape it's hard to see

all the turbulence caused by the sharp

edges of the box shape but you can see

on the smooth-edged box shape one sort

of like the normal screwdriver handle

there is swirling there's sort of a

backwards flowing region of fluid so

that indicates that there's low-pressure

there because that fluid is actually

flowing backward toward the screwdriver

handle you've probably seen a similar

phenomenon if you've ever driven behind

a pickup truck that's got like dried

leaves or like a plastic bag in the

pickup bed you'll notice that as the

truck drives along the bag and leaves

are not blown out of the truck in fact

they're blown forward they're blown

toward the cab of the truck because the

air

circling or circling around the back of

the tailgate and blowing backwards and

that's actually what causes drag on in

cars if you're interested in playing

with fluid dynamics and a fun sort of

way I recently put plans online to build

one of these fluid demonstrator discs

and this is actually the project that I

showed recently at Maker Faire this is a

super easy build it really only takes

about an hour spread out over a whole

weekend and you can get all the parts

online for it the disk is filled with

this ray of scopic fluid that I

mentioned that you can buy online and

when you spin the disk the motion of the

top and bottom surfaces of the disk

agitate the fluid and you get turbulence

out at the edge here in the middle you

still have that smooth region that

laminar flow region that was causing all

the drag and allowing us to levitate

screw drivers ok see you next time byebest way to earn money from home, make instant money online absolutely free, trusted online money making sites, online income site, best online earning, money online, earn money from home, earn dollars online, earn money online, earn money online 2019, earn money online by typing pages, earn money online daily, online work at home and earn money, online earning, earn money online free, online money earning sites, earn real money online, e commerce ideas to make money, easiest way to earn money online, best way to earn money online, make money from home, make money online free, money making sites, earn from home, real ways to make money from home, online income ideas, make real money online, top online earning websites, earn money online fast, top 10 money earning websites, earn money without investment, earn money online for students, best sites to earn money, make money online 2019, earn easy money online, earn money online instantly, real money earning sites,