08x03 - Inflatable Slides, Swing Burpees, Kitesurf Rolls

[bunniefuu]

DALLAS (off-screen): This

is the Science of Stupid.

Yes, this is the show that

stirs serious science into a

petri dish of stupidity.

Behold the actions of the

misguided as they tangle with

the rules of science and

feel the force of physics.

We'll explain what went wrong

and why with the help of

fascinating principles

such as angular momentum,

traction and those

naughty little playmates,

center of mass and gravity.

Hold on tight, it's

the Science of Stupid.

In this episode we'll use lift

force to pull off incredible

tricks and whatever that

was, learn how kinesthetic

awareness A*DS balance

and we'll be analyzing the

molecular structure of

rubber but first this.

Since their invention in the

1930s snowmobiles have become

surprisingly versatile, you

can now see them drag racing

across grass, hurtling up near

vertical mountain sides and

even riding over the

surface of lakes,

but there's one thing we haven't

quite got them to do yet.

DALLAS (off-screen):

And that's to fly,

which makes

dropping off a 1,600-foot cliff

a really bad idea and even

if you pack a parachute

like this chap, your snowmobile

will never forgive you.

There's around 14,000

snowmobile related injuries

per year in North

America alone,

so why on earth would you risk

driving over a cliff on one?

Extreme sports enthusiasts

call it 'hucking',

we scientists call it

absurdly dangerous because we

appreciate gravity, vertical

velocity and impact force.

DALLAS (off-screen): As soon

as the combined center of mass

of a snowmobile and rider

goes over a cliff edge gravity

acting on it will

rotate the snowmobile.

A faster launch gives gravity

less time to do this and a

landing area with a

steep gradient allows the

snowmobile's vertical velocity

to be reduced gradually,

lessening impact force but if

the landing area is too flat

it's gonna hurt.

Thus counterintuitively a

steeper landing area can

actually be less dangerous

relatively speaking but let's

start with a launch and to

avoid a nosedive our huckers

will want to approach

with plenty of speed.

DALLAS (off-screen):

Uh, yeah. A little slow.

MAN: Oh.

DALLAS (off-screen): Meaning

loads of time for gravity to

cause a rotation.

The soft snow did

reduce the impact force,

then the hard snowmobile

did the opposite.

MAN (off-screen): Oh.

MAN: Oh.

DALLAS (off-screen):

So, how about a run up?

Yeah, a bit like that.

Only longer and

with more throttle.

Okay, well don't forget it's

also possible to decrease

impact force simply by choosing

a steeper landing area.

DALLAS (off-screen): Like

this one but even steeper.

With a landing area about

20 degrees steeper he would have

gradually reduced vertical

velocity and lessened the

impact force, but we would

have missed out on that

excellent cartwheel.

Right, are you sure you

still want to do this?

Okay, well, as long as

you've considered gravity,

vertical velocity and hold on,

is that landing steep enough?

Yeah, no I didn't think so.

And now we briefly turn our

backs on the tribulations of

the misinformed and

applaud the triumphant.

Philippe Petit, the famed

Twin Towers high wire walker,

or funambulist, said, 'Limits

exist only in the souls of

those who do not dream.'

Well, Philippe, I'm actually

quite happy with a few limits because I'd never

dream of doing this.

DALLAS (off-screen): Meet

Aisikaier Wubulikasimu

attempting the Guinness World

Record Title for the faster

high wire walk between

hot air balloons.

To succeed he must successfully

cross this 59-foot

long scaffold which is

constantly moving

and with 38.5 seconds on the

clock he set the world record.

Now, if you are considering

hiring 60 feet of scaffold,

two hot air

balloons, plus crew,

and a big long

pole think again.

DALLAS (off-screen): Because

for every expert funambulist

there are millions of these

guys discovering that

limits do exist.

But hypothetically speaking

what science would we need to

beat Aisikaier's record?

Let's find out.

DALLAS (off-screen): Our

funambulist must keep his

center of mass over a narrow

moving base of support or

he might rotate.

His long pole distributes

mass away from his center,

which increases his moment

of inertia and helps resist

rotation, and he has

exceptional kinesthetic awareness.

This is the capacity of nerve

endings to sense the tiniest

movements of the limbs,

allowing him to maintain

focus dead ahead.

As our friend Philippe

once remarked,

'Trust your feet, let them

lead you. They know the way.'

Although, I'd argue

it does depend on

who the feet belong to.

DALLAS (off-screen): Our first

wannabe record breaker isn't

even on his feet.

Will that work?

It seems unlikely now.

Stretched along the pole his

moment of inertia is too low.

Yeah, alright.

At least he's had a go.

Ah, now stretching your arms

out does increase your moment

of inertia, a bit like a pole.

No wait, he's just balancing

on his friend and physics

isn't kind to cheats.

Still, at least his narrow

base of support wasn't high up

and moving about.

His is.

MAN (off-screen): Oh.

DALLAS (off-screen): Oh,

which is why he fell off.

Somehow this body shape

doesn't suggest a man in touch

with his kinesthetic

awareness.

More in touch with

that sharp rock.

Okay, we've studied

moving bases of support,

kinesthetic awareness and

moment of inertia but I don't

think we'll be breaking

that record anytime soon.

Ah, tubing.

What a thrill but can

you guess what science it will reveal?

DALLAS (off-screen): Did you

work out which scientific

principle these tubing

kids are about to enjoy?

Is it wave mechanics?

No, it's undulation in fish.

When sensing a threat,

like a noisy motorboat,

some fish can thrust out of

the water by raising their

pectoral and pelvic fins and

simultaneously undulating

their flexible bodies.

In this case undulating

into a child.

Don't worry, he was fine

and so was the child.

And now my gentle and learned

viewers, a quick question.

What material links.

DALLAS (off-screen): The

ingenious biology that

allows trees like

this to heal themselves when

distressed and

this kind of thing.

MAN: That was crazy.

DALLAS (off-screen): Yeah,

that's a fair assessment.

The answer is rubber.

In its natural form

it's made from latex,

a liquid tapped from particular

plant and tree species.

It seals their wounds but for

thousands of years humankind

has been pilfering it

to make things stretchy,

bouncy and grippy.

Here's how that works.

DALLAS (off-screen): Rubber is

elastic because it's made up

of long weekly connected

chains of atoms that can be

squished or pulled out

straight before returning to

their original shape.

Some products, like tires, are

made with vulcanized rubber,

where the rubber is reacted

with sulfur to form atomic

crosslinks that bind

the chains together,

resulting in a material that's

more rigid and durable and so

can be formed into tread

patterns that give tires

improved grip.

Among the first to appreciate

the elastic quality of natural

rubber's atomic chains

were the Mesoamericans,

who over 3,500 years ago

used rubber ba*ls in their

ceremonial game, Ollama.

DALLAS (off-screen):

This isn't Ollama,

but those elastic chains

also allow rubber balloons to

stretch when filled with

air and become floaty,

who doesn't love

floaty rubber?

Well, Jasper here.

He hates it.

Vulcanized rubber and you can

make tires that are tough and

grippy, even when these lads

are doing all they can to

loose grip and drift.

Play time is over chaps but

that tire still hasn't lost

its grip.

What's going on here?

Ah, you dropped

your credit card.

MAN: It is so slippy.

DALLAS (off-screen): Well,

don't worry because just like

tires shoes often have

vulcanized rubber soles

offering plenty of grip

but not quite enough.

What you need now

is a wet suit.

The same rubbery properties

allow them to stretch and trap

a layer of body warmed

water next to the skin,

although usually

not quite that much.

Okay, how are we doing

at the harbor wall?

Oh, so close.

MAN: You will have to hurry up

because the tide is coming up.

DALLAS (off-screen):

Where's a rubber dingy when you need one?

In the 1800s as engineers

searched for cost effective

alternatives for horses and

steam for powering public

transport, wind in the form

of large kites were seriously

considered but now after two

centuries of development we

still don't have

kite powered buses.

DALLAS (off-screen):

But we can do this.

The board flip.

Yes, the butter slide.

A nice fence for a grind.

Watch out for my post turn and

then there's this, the roll.

An airborne inverted

spin, nice work.

See you next time.

That was an advanced

version of a roll,

a core kite surfing trick

with plenty of variations.

Kite surfers can front roll,

back roll, roll and nose grab.

DALLAS (off-screen):

There are all sorts of ways of mixing it up

and that wasn't

one of them.

To perfect the right kind of

airborne rotation for a kite

surfing roll requires a

mastery of angular momentum

and lift force.

Here's the roll 101.

DALLAS (off-screen): As wind

flows over a kite's wing-like

shape it generates lift force

pulling him across the water.

On launch he throws his body

backwards generating just

enough angular momentum

for a complete rotation.

To land he steers his kite

downwards and ahead of him,

this increases lift force

in the direction of travel,

so he avoids sinking.

It is complicated stuff

to deal with all at once,

so first let's just practice

using lift force to get a

little air.

DALLAS (off-screen): Okay,

we've got that covered.

Now, let's add some angular

momentum for the roll.

I said 'some'.

I mean, he did get enough

angular momentum for one

rotation, but he didn't

have time for two.

Okay, let's work

on the landing.

Now, can you remember

which direction we need to send that kite?

DALLAS (off-screen):

No. Quite the opposite.

He actually aced the angular

momentum but if you want to go

in this direction,

like your board,

and your kite is steered

down and in this direction,

it's not going to happen.

Okay, last chance.

Arguably worse.

Lift force in wrong direction,

too much angular momentum,

very sinky landing.

DALLAS: The slide.

Momentum fueled fun in its

purest form and possibly its

most varied.

DALLAS (off-screen): Form

the classic playground slide.

To the water slide and

my personal favorite,

the inflatable.

There are all sorts of slide-y

ways to enjoy and be hurt by

momentum but the inflatable,

what with its air-filled

squishiness should

be one of the safest,

provided of course you check

the guidelines to ensure you

are of the appropriate

age and size,

and study the

relevant science.

DALLAS (off-screen): The steep

angle of the slide combined

with the low coefficient

of friction offered by the

plastic surface, and

lubricating water,

allows our slider to build an

enjoyable amount of momentum.

Momentum is

proportional to mass,

so thanks to her relatively

low mass what momentum she

gains is gradually reduced at

the bottom as the air-filled

barrier compresses,

lessening the impact force.

Even inflatable slides can

be dangerous when used by the

wrong person, a combination

of steep gradients,

slippery plastic and

lubricating water can produce

a fun amount of momentum for

little masses but increase the

mass and it can

quickly get unfun.

WOMAN: You might

want to back up.

DALLAS (off-screen):

Oh, why's that?

Ah, I see.

WOMAN: That was graceful.

DALLAS (off-screen): Not to

mention informative because

here we learn how a greater

mass plus lubricating water

equals too much momentum and

in this family the punishment

for excessive momentum

is swift and degrading.

WOMAN: Yay.

DALLAS (off-screen): Here a

young adult is about to test

another way of

reducing momentum.

It worked.

Wet slide, low friction,

flight, no friction.

Grassy ground, some friction.

Chair in face, impact force

but the best thing about low

friction surfaces is you

don't have to reach the top.

MAN: Come on.

One, two, three. Go.

DALLAS (off-screen): To enjoy

a wonderful graceful slide.

Do you yearn for a one stop

method of combining high

intensity strength training

with aerobic conditioning?

DALLAS (off-screen): Well,

look no further than the

burpee, it works the arms,

chest, quads, glutes,

hamstrings and abs and if

you want to make it even more

hard-core try this.

No but, like, together and

there it is, the swing burpee.

Looks impressive but we've

all got to start somewhere.

MAN: Oh.

DALLAS: Now, I'm not

recommending this but there

is a logic.

Think of the swing as a kind

of bullying metronome that

keeps you moving to a beat and

then trips you up if you

can't keep pace.

To avoid that we

must study friction,

air resistance and

simple harmonic motion.

DALLAS (off-screen): The

pendulum movement of a swing

approximates simple

harmonic motion,

wherein the seat repeats its

path moving slower towards the

top and faster

towards the bottom.

Our burpee-ist must coordinate

perfectly with this motion,

which gets harder with

every swing because as air

resistance acting on

the seat and rope,

and friction at the

pivots slow it down,

the arcs become shorter, so he

needs to speed up to keep up.

He was an expert, and this

is a dangerous activity,

so please don't attempt to

turn your local playground

into a gymnasium.

Alright now, as per the

science we start with getting

in perfect sync with that

simple harmonic motion.

DALLAS (off-screen):

Lovely leap.

Bit eager on the push up.

Now, I know I said a swing

seat moves faster at the

bottom of the arc

but not that fast.

Now we're talking but remember

with every swing it gets

a little harder.

A combination of

friction here,

in this case his tight shorts

and air resistance here on

this floppy seat slowed the

swing and twisted it sideways

so he couldn't keep

up or fit through.

It's okay dog.

No CPR required but

thanks for the offer.

Once you're in perfect harmony

going forwards you could try

backwards but I

wouldn't advise it

cause with air resistance

and friction already reducing that arc it

helps to see what

you're jumping over.

WOMAN: Yeah, I'm good.

DALLAS (off-screen):

Debatable.

WOMAN: Thank you.

DALLAS (off-screen):

That wasn't a compliment.

Still at it?

WOMAN: I'm so afraid!

DALLAS (off-screen): Well,

don't feel bad because a

simple harmonic motion is

not as simple as it sounds.

Greek philosopher Pythagoras

first proposed around earth,

around 500BCE, and yet after

2.5 millennia of scientific

exploration, circumnavigation

by sea, air and space,

plus the mere fact that the

sun goes down here at the same

time it pops up somewhere else

there are still people aplenty

who just don't buy

that we're not living on a pancake but hey.

If it wasn't for people who

didn't listen to science the

next 30 seconds

would be very boring.

(music plays through credits).