06x11 - Ninja Grip, Rope Swing and Parasailing

[bunniefuu]

[Dallas off-screen]
This is the Science of Stupid.

Yes, this is the show where we find the
complex science in complete stupidity

as we attempt to make
sense out of nonsense.

Our team of test subjects will challenge
the boundaries of scientific knowledge,

so you don't have to.

With their help, we'll demonstrate the
science behind some key

principles such as freezing level.

Torsional damping.

And aquatic oscillations.

So, pay attention.

It's the Science of Stupid.

In this show
we'll explore lift.

Friction.

And circular motion.

But first this.

In the olden days, before smartphones,
VR headsets and hoverboards,

humans had to make their own fun, and
they did this by meeting up with friends

and doing fun stuff.

Like swinging off banks.

[man] Ohhh yes! Yes! Yes!

[Dallas off-screen] And if that doesn't
seem exciting enough,

you could always add a quadruple
backflip to your bank swing.

He literally hasn't thought about social
media for, like, three minutes.

Oh, nice matching bandanas.

[man] Remember, lean back and...

...pull your knees
up to your chest.

[Dallas off-screen]
But, before you go big.

[man] There you go.

[Dallas off-screen] It's
always best to start small.

Perfect. Perfect-ish.

Swinging on a rope is one of those
pursuits that has been providing

mankind with entertainment for thousands
of years, and what have we learnt?

Well, letting go
above water is easy.

Landing back on the
bank is a bit trickier.

To avoid mishaps, our man must ensure
there is a high coefficient of friction

between hand and rope in
order to maintain a grip.

Since he and the
rope form a pendulum,

he must start from high
enough to ensure he has

enough gravitational potential energy to
return him to a safe landing spot.

A good swing onto a bank should also
factor in the tensile strength

of the rope and branch, the trajectory,

and most importantly, an exit strategy.

Most failures when swinging onto a bank
are due to errors in judgement.

So, if you want to land back on the bank
with dry socks,

you need to know all about trajectories,
tensile strength,

and gravitational potential energy.

[man] Here we go.

[Dallas off-screen] He's got his
gravitational potential energy

about right, but his exit
strategy needs work.

He should have let go
about there, and he doesn't.

[man off-screen] Oh, dad!

[Dallas off-screen] And
now, there's no way back.

[man] Help.

[Dallas off-screen] Now, remember, the
structural integrity of

a swing is always
a key consideration.

[man] I'm not going to risk it.

[man] Oh, no. God.

[man] That's why I didn't do it.

[Dallas off-screen] There's a single
point of contact between rope and stick

so, when he swings, the high
pressure at that point leads to

a structural failure.

And a very sore back.

His helmet suggests he's well prepared,
but has he calculated his trajectory?

Well, I think that answers
that question nicely.

The helmet protects
his head from knocks,

but not knees from
stinging nettles or his

butt from getting wet.

What's your assessment?

[man] That was a fail.

[Dallas off-screen]
Yeah, I concur.

So, next time you fancy being the king
of the swingers,

don't forget your science.

And definitely don't do this.

Because it really hurts.

Alright, let's see how
that first guy's getting on.

[man off-screen] Good.

[Dallas off-screen]
Looks like he's still stuck.

[man off-screen] Can you
build up momentum somehow?

Yeah.

No dad, you've got to wrap it.

[Dallas off-screen] Your son's science
is a lot better than your swinging.

Right.

Now it's time for us to look at the
natural world, and today

we're gonna be studying something that
we can't live without

but could sometimes do without.

[man] We're going to get wet?

Right, here we go!

[Dallas off-screen] I am,
of course, talking about rain,

because while it can bring
untold joy to the uninitiated,

it can often
be quite disruptive.

Although, if you have a massive tractor,
you should be just fine.

[screams]

[laughter]

[Dallas] Did you know that the greatest
rainfall recorded in a 24-hour period

occurred on Réunion Island
in 1966 when 72 inches

poured down on
the Foc-Foc Plateau?

That's enough water to completely
submerge the average American man.

With rain like that, I don't think an
umbrella is gonna be much use,

but understanding the
science never hurt anyone.

Rain is part of the hydrologic cycle
that begins when water evaporates

and forms clouds
in the atmosphere.

Water vapor condenses on
micrometer-size particles of dust

floating in the atmosphere to form cloud
droplets

just a few hundredths
of a millimeter in size.

Within the cloud, droplets collide and
combine until they're heavy enough for

gravity to pull them down.

Below the cloud, as long as the droplets
are big enough to survive evaporation

in the warmer air, they will eventually
reach the ground as precipitation.

So, rain comes about because of
evaporation,

condensation and precipitation.

But the science doesn't stop
there, because after it falls,

it can stick around on the ground and
become a pretty effective lubricant.

And the most important thing to
understand about a lubricant

is that it can lead to a loss of
friction.

The rainwater forms a thin layer between
the players' feet and the ground,

meaning when they attempt to kick, the
standing leg does not have enough

friction to resist the torque
from the swinging leg,

giving their friends
a hearty chuckle.

I always find that high-speed parking in
the rain is best avoided.

And that's why.

Car tires are designed to displace
water, but there's a limit to the amount

of water that can be displaced, and
lower friction becomes a

problem on a corner where lateral forces
are the order of the day.

Of course, the heavier the rain, the
more water there will be on the ground.

And with more water, high speeds lead to
hydroplaning

and a severe loss of
friction.

Perhaps in future, this couple should
stick to public transport.

Coming off the bike at
nearly 70 miles an hour,

the low friction between their
leathers and the wet road

meant it took
nine seconds to stop.

More than enough time to contemplate the
properties of rain.

Pay attention as this patriotic pool
partier is about to demonstrate a

scientific principle,
but can you guess which one?

[man] Party time, baby!

[Dallas off-screen] Have you guessed
which scientific principle

is about to disconcert
this poolside reveler?

[man off-screen] Woo!

[Dallas off-screen] That's
right, it's turning effect.

[man] Party time baby!

[Dallas off-screen] The diving board
acts as a moment arm to increase

the turning effect of
his weight and momentum.

Unfortunately, this turning effect is
enough to overcome the material strength

of the board's fixings, really
getting that party started.

[woman off-screen] Oh my God.

[Dallas] Going on a tropical holiday
might seem like the stuff dreams are

made of, but when you're bored of
sunbathing and you've finished reading

A Brief History of Time,
what do you do?

One option is parasailing.

Not only is it invigorating, but it's
also a great way to take in the views.

But as Stephen Hawking once wrote, the
universe does not allow perfection.

[man] What the ****!

[Dallas] And your holiday in paradise

might end up with a trip to the
hospital.

[man] Urgh.

[Dallas] In 2002, the Swede Berne
Persson parasailed continuously for a

record-breaking


which is about a day and
ten minutes too long for me.

But, should you be stuck by
an urge to take to the skies,

I suggest very strongly
that you consider the science.

Parasails are air foils which generate a
lift when moving

beyond a certain velocity.

They're accelerated by a boat using a
tether held under tension.

Once launched, the boat needs to be
pulling him at between


required lift, otherwise,

the high drag coefficient of the sail
will send him into the sea.

So, it's a delicate balance of lift and
drag in the air to keep you aloft.

But the water can be a real drag before
you even get there.

Perhaps we'd have better luck getting a
proper launch from good old terra firma.

Yeah, that's not
a proper launch.

Trying to keep up with the accelerating
boat proves tricky

and he is tugged over.

The resulting friction means his chances
of flight are pretty much zero,

but his chances of exfoliating
his face are very good indeed.

This looks promising.

He just needs to remember
to keep up with that boat.

[man] Oh [bleep]!

[Dallas off-screen] He actually
accelerates faster than the boat

which means that cable isn't at tension,
so he attempts to jump up

before his sail has
generated enough lift.

It's only when the cable goes taut that
he's launched into the sky.

[man] [bleep]!

[man off-screen] No.

[Dallas off-screen]
Before a headfirst.

Dunk in the drink.

[man] Oh my God.

[Dallas off-screen] Let's check
back in with our dynamic duo.

Yup, still not airborne,

but nothing a little
added velocity can't fix.

Well, points for style.

Right, it's time for
today's science lesson.

That part of the show where we like to
take apart one

specific scientific
principle to see how it works.

So, who can tell me what the
following have in common?

[man] Let's see what you've got.

[Dallas off-screen] This
golf-buggy-driving granny.

[man] There you go.

[Dallas off-screen]
This hard-running hamster.

And these rowdy
roundabout riders.

[man off-screen] Oh [bleep]!

[man] Help!

[man] I quit!

[Dallas] Did you guess that they were
all to do with circular motion?

Well, if you did, give yourself a gold
star and a good, firm, pat on the back.

Now, let's get to
grips with the science.

As these skaters spin, they are objects
in circular motion,

constantly changing the direction
component of their velocity.

This requires the constant application
of a force known as centripetal force,

while the object following the curved
path feels a centrifugal force

to the outside.

It's worth nothing that, without all
that important centripetal force,

your object is free to carry on in a
straight line rather like this.

Now, it's time for a test to see who's
been paying attention.

Question one.

What are objects in
circular motion doing?

To make things a bit clearer,
we've hired this high-speed

Christmas tree
decorator to demonstrate.

He's maintaining his circular motion by
constantly changing the

direction component of his velocity.

And what could be
more festive than that?

Question number two.

What makes something
move in a circle?

[man] Oh!

[Dallas off-screen] The answer,
of course, is centripetal force.

As the roundabout speeds up, the boy
experiences enough centripetal force

to pull his body outward for a
classic leg sweep.

Okay, third and
final question.

What force does an object
moving in a circle experience?

This kid is going to show us.

As he runs, he gives the giant hamster
wheel angular momentum,

but when he trips, that angular momentum
turns on him

and he experiences
centrifugal force

pinning him to the outside of the
circle.

For a while, at least.

So, there ends our
lesson on circular motion.

However, I suggest that, unlike this
donut,

you don't take what you've learnt
out onto a public road.

[man] Wee! [inaudible].

[Dallas] So many things in science are
mysterious or complicated,

from the expanding universe
to the large hadron collider.

But powders, I think I know.

We see them every day, from the talc you
use after your morning shower

to the flour that goes into your toast.

They're simple.

[man] Sam a bright boy.

[Dallas off-screen] And
they're useful for everything.

From science experiments.

To fire extinguishers.

[man off-screen]
Happy birthday to you.

[Dallas off-screen] But the thing you
need to remember about powders is.

[man] Woah, my gosh!
What was that?

[woman] I forgot
about the powdered sugar!

[Dallas off-screen] They're a bit more
complicated than you'd probably imagine.

Powder, as we are beginning
to learn, has many properties

beyond being a cake ingredient.

Powders are collections of
tiny particles

which can act like a fluid
when agitated.

Powders stick to things and clump
because of the van der Waals force,

which is too weak to have an effect on
larger and heavier particles.

Powder particles have extremely high
surface area to volume ratios,

so they experience a lot of air
resistance which makes them float.

That high surface area also makes them
potentially flammable,

thanks to their greater contact with
oxygen,

which makes sense when you learn

that there are about 2,000 dust
explosions in factories and refineries

across Europe every year.

Yeah, powders and fire are definitely
not to be trifled with.

And one of the reasons for this is
because of the way

powder disperses in air.

And to illustrate this point, I have
commissioned our Welsh

research unit to demonstrate the
principle

using only a supposedly
blocked pipe and an unsuspecting victim.

[laughter]

[Dallas off-screen]
Good work, team.

The unwitting test subject blows heavily
into a powder-filled pipe.

His air blast agitates the powder and
shows how easily

it's suspended in the air.

Mr Bigglesworth was also keen
to do some research,

just don't expect him to tidy up.

[man] He's covered in flour.

[Dallas off-screen] Powder adheres to Mr
Bigglesworth thanks to

van der Waals forces and electrostatic
attraction.

But, when he shakes, the acceleration of
his fur transfers kinetic energy to

the particles, causing the flour to
disperse and makes a bit of a mess.

[man] Get back, Dad!

[Dallas off-screen] But
it's nothing compared to this.

This corn silo has suffered a massive
structural failure and is pouring tons

of grain onto the ground.

This is bad.

But not as bad as that.

[man] Son of a g*n.

[Dallas off-screen] When the silo
ruptures,

it reveals the liquid-like
flow of powders.

Then the structure collapses
creating a dust cloud

and snapping an electrical cable.

The high surface area to volume ratio of
the particles

presents a huge surface to
the oxygen-rich atmosphere.

All it needs is
a little spark.

It's not the sort of
thing you see every day.

[man] Another day at the farm.

[Dallas off-screen]
Or maybe it is.

First, it was yo-yos, then it was
planking,

and now the latest fad seems
to be ninja-themed gameshows.

They look fun, but if you want
to be a champion,

you're gonna
have to train pretty hard.

This guy from Germany has
been preparing all his life.

He's even made his own course
in his parents' garage.

But, sadly, not everyone has the
resources of our German friend.

Now, I am no expert, but what I do know
is that, if you want to be good

at warrior games,
you're gonna need to get a grip.

The competitor must ensure he
has a good grip on each hand-hold

so he doesn't fall, making a hook with
the fingers

so he doesn't need to rely
on friction to keep him in place.

Speed is of the essence, but he needs to
minimize the vertical component of

movement, avoiding increasing downward
force at the bottom of the swing.

It's also important to maintain body
tension, as keeping a strong core will

help him control
his trajectory.

Right, there you have it.

Quite a lot to take in, I know, but
thankfully our researchers

have been working hard in training and
are ready to put theory into practice in

our very own ninja amphitheater.

First up, Chanelle.

And she'll be facing
the unstable bridge.

[man] Yeah.

[Dallas off-screen] Thanks to her
well-trained muscles and core strength,

-she's making this look easy.
-[man] Yes.

[Dallas off-screen] But
this obstacle is unforgiving.

[man off-screen]
Come on, finish it up.

-Oh.
-[woman] Ow.

[Dallas off-screen] Making a hook with
her fingers would normally be enough to

secure her to the board and
keep her hanging.

-[man off-screen] Come on, finish it up.
-[Dallas off-screen] But since the block

is only attached at a single point,

her grip behind that point
makes it pivot and tilt so her

hooked fingers don't provide
enough friction.

[man off-screen] Oh.

[Dallas off-screen]
This fine specimen is Dom.

He's the man in
charge of the research team,

but he likes to conduct most
of his research in private.

-And that's why.
-[man] Oh.

[Dallas off-screen] He has excellent
grip strength on the first bar,

replicates this on the second, but
unfortunately grip strength is

worth nothing without enough momentum
and the right trajectory.

So, that's ninja grips.

Yep, harder than they look.

Well, after all that, I feel a little
bit like the German theoretical

physicist Werner Heisenberg
when he said,

"What we observe is not
nature itself,

but nature exposed to
our method of questioning."

♪ ♪