07x08 - Inflatable Tube, ATV and Animals

[bunniefuu]

[Dallas Campbell]
This is the Science of Stupid.

[electricity crackles]

[klaxon blaring]

-[man yelping]
-[Dallas] Yes,

this is the show that adds
a drop of science

to a test tube of stupidity.

Witness the work of idle hands...

and misinformed minds

as they take jaw-dropping risks

for the betterment of science.

We'll examine what went wrong

and why with the help
of science's prickliest principles,

such as inverted pendulums,

thermal expansion,

and your friend and mine,
turbulent flow.

It's half an hour of pain...

-[man screams]
-...for a lifetime of gain.

Standby...

for the Science of Stupid.

[electricity crackles]

In this episode, we'll be looking
at hydrodynamic drag

-[man] Oh!
-[Dallas] ...and impact,

quadrupedal locomotion and impact,

viscosity and soggy pants.

But first this.

[glass shatters]

[electricity crackling]

Take one large inflatable tube

and one hand-crafted ramp built of snow

and you've got the perfect tonic

to blast away those winter blues.

-It's a great laugh...
-[boy] Aah!

-[man laughing]
-...for your family.

♪ ♪

A wonderful way to get close to nature.

-[man] Woo! Oh!
-[woman] Aah!

[Dallas] And you'll meet
new friends along the way.

Hello!

[laughter]

Okay, so launching oneself off a
ramp in a tube can be

rather dangerous,

That combination of low-friction snow
and steep gradient

tends to result in a lot of momentum.

Key to a safe flight lies partly
in launch angle and posture.

♪ ♪

Sitting his center of mass
can be towards the back,

so on take-off a turning effect leads
to angular momentum,

rotating him backwards.

Lying down his center of mass
is towards the middle,

but if the ramp is steep,
the tube could land back-end first,

and the compression of the tube could
bounce him into a forwards rotation.

Letting go isn't smart as the lower
density tube is more effected

by air resistance,
so he will go further.

So, in laymen's terms,
lying can keep you nice and stable,

sitting up can lead to an excruciating
backwards rotation.

So simple, who could mess it up?

♪ ♪

Loads of momentum, but is he...?

Yep, he's sitting up.

-[man] Whoa! [screams]
-[laughter]

[Dallas]
As predicted, a backwards rotation.

The low coefficient of friction
between the tube and snow means

that he reaches about 16 miles an hour.

And if he'd actually made the ramp,
he might have landed on the road.

-[man] Whoa!
-[laughter]

-[Dallas] So sitting back is a problem.
-[dog barking]

But lie down and you'll be fine.

[laughter]

Well, not always obviously.

She let go and as her legs
rebounded off the bouncy tube,

she gained angular momentum,

and then pivoted gracefully on her face.

[laughter]

And what soothing words of sympathy
will her companions bestow?

[woman off-screen]
She literally ate snow!

[Dallas]
Ah, yes, those ones.

Now your next problem is ramp angle.

-Is that one a bit steep?
-[man] Right there! There it is!

[man off-screen]
Get him, Greg!

-[laughing]
-[whistle trills]

[Dallas]
Yeah, yeah. It was.

See here how the 45-degree ramp tilted
his tube so it lands back-end first,

bouncing his legs
into a lovely 360-degree flip.

[laughter]

But if all that air-filled bounciness
is causing you problems.

[man] Yeah!

[Dallas] All right, well then.

Isn't it better just to ditch the tube?

-[woman off-screen] Oh yeah!
-[man screams, grunts]

[Dallas] Not really, no.

Remember, your tube is affected
by air resistance more than you are.

-[woman off-screen] Oh yeah!
-[man screams, grunts]

[electricity crackles]

[metal creaks, clatters]

In the 1960s roughty-toughty
Canadian John Gower built

the very first ATV,
or all-terrain vehicle.

It was powered by just
a couple of old chainsaw engines,

but it was truly all-terrain
because it was amphibious.

Fast-forward 60 years...

and the modern ATV can have more
than ten times the horsepower.

[man shouts, muffled]

But sadly it's not amphibious.

Alas, being able to swim never became
a standard feature of the modern ATV.

In fact, driving through
any body of water on one can be

scientifically problematic,
and here's why.

♪ ♪

An ATV and driver have
a high combined center of mass

relative to the wheel base,

so are prone to tipping,

this can be challenging in water.

With enough speed the water,
pushed downwards by the wheels,

can generate lift,
balancing the ATV's weight,

allowing it to skim the surface,

but if it's not going fast enough,
it will start to sink.

Hydrodynamic drag
will dramatically slow it down,

and that high center of mass
will pivot outside the base.

Now, with hydrodynamic drag
the faster you go

and deeper the water, the more you get.

♪ ♪

So a nice shallow puddle is fine.

[laughter]

That wasn't quite as shallow
as I'd thought.

He hit a hidden deep patch
at high speed,

resulting in a big slap of drag
and a classic turning effect.

[laughter]

So, how about going a little slower.

[man off-screen]
Go!

[Dallas] Like this.

Except without the three-foot drop.

All right, let's try faster.

Remember, with enough speed,
an ATV can skim across the surface.

[man]
Oh!

[Dallas]
Like the first bit of that.

[man off-screen] I'm ready.

[Dallas] At 28 miles an hour,
he was skimming,

keeping hydrodynamic drag
to a minimum until he slowed down,

and then hit the mud bank.

[man]
Oh!

[Dallas]
Otherwise textbook.

So, it may be best to sell the ATV and
buy something a little less top heavy,

like this custom four-by-four.

I mean, look at it go.

And it absolutely smashes it
in the water.

Eh...

That was a waste of money, wasn't it?

We didn't really go into getting out
of the water in the science bit, did we?

So, I'm, I'm just gonna go
over... over here for a bit.

If you don't mind, I'll see you later.

[electricity crackles]

[metal creaks, clatters]

[Dallas] An evening stroll with Fido,
but what science will it reveal?

[glass shatters]

[electricity crackles]

[Dallas] Did you guess the science
that they're about to show us?

[woman] You're not going anywhere.

-[Dallas laughs] Yeah, but she is.
-[dog barking]

[woman] Ow!

[Dallas]
Thanks to tension.

When the lead reaches its limit,
it's under tension.

The force from Fido's momentum
is applied to her,

she accelerates, trips on a pumpkin,

and collides with a scarecrow.

[woman] Ow!

-[Dallas] We've all been there.
-[woman] Jeffrey!

-[man] Where are you going?
-[dog barks]

[electricity crackles]

[whirring]

[Dallas] We h*m* sapiens frequently seek
to distinguish ourselves

from our lowly animal cousins,
first it was complex language

but it turns out some monkeys
are really rather eloquent.

Then it was the use of tools,
except even crows do that,

but, a-ha, can animals do stairs?

Well, this one can't.

-He just doesn't have the legs for it.
-[puppy yelps]

To be fair, while stairs were
designed for the human

two-legged, or bipedal gait,

it's mainly the smaller or infantile
versions of our four-legged,

quadruped friends who tend to struggle.

But it can be done,
and to show how,

here's a little dog
with a lot of science.

Quadrupeds have hind legs
designed for propulsion...

which function like levers
to help them bound up stairs,

while their front legs are
designed to absorb impact

and must do most of the work
controlling the descent.

Descending can be riskier because
gravity is trying to speed them up.

Right, come on g*ng,
you've heard the science,

now show us bipeds
what you're made of.

Paws up, who's first?

Old Keith here is a Corgi,
long barrel-like body,

tiny legs, it's an uphill battle.

-[Keith growls]
-[woman off-screen] Oh!

[Dallas] And the battle he's lost.

Less proportionally
challenged pooches...

-[Keith whimpers]
-[Dallas] Sorry.

...might use their propulsive
hind legs to bound up the stairs.

But old Keith, well...

-[Keith growls]
-[woman off-screen] Oh!

[Dallas]
Oh, what was he thinking?

Now this doesn't look right at all.

Oh, I see.

Now, Suki here is cheating really
with her powerful muscles

and clingy catty claws.

It's just arrogant.

So, that's going up.

How about going down?

-[man off-screen] Come on.
-[kitten meows]

[Dallas off-screen]
Well, Mittens is a kitten.

So that's one small step for a man,

but a giant leap for--

-[body thumps]
-[Mittens yowls]

-Oh, Mittens!
-[man laughs]

Working downwards,
those front legs absorb impact

and control her descent,

but Mittens overshoots a step
and gravity takes her down.

Luckily, her flexible spine does help
her soak up the impact.

-[Mittens yowls]
-[man laughs]

[Dallas] Mittens, take a leaf out
of Brian's book.

He's having a breakthrough.

Well done, Brian.
You are a master of gravity.

[girl off-screen] Mommy!

[Dallas] No animals were hurt
in the making of this program,

but some were extremely embarrassed...

-[woman off-screen] Oh!
-[Dallas] ...especially Keith.

[bell rings]

-[clattering]
-[liquid burbling]

Right, class, it's time
for your science lesson,

the part of the show where we focus
on one particular scientific principle.

Now, there will be a test later,

but first can you guess what today's
principle is from these cryptic clues?

It's sometimes runny...

and sometimes thick.

[man off-screen]
Whipped cream challenge!

[Dallas]
And when it's thick...

[laughter]

...it's also sticky.

[man off-screen]
He's stuck!

[Dallas]
I just said that.

The answer, of course, is viscosity,

scientifically defined
as a measure of a fluid's

resistance to deformation
under sheer stress.

How viscous a fluid is depends
partly on how much internal friction

there is between its molecules.

For example...

Water has low fluid friction,
so low viscosity,

and it's easily deformed
by sheer stress.

Honey has more fluid friction,
higher viscosity,

and so it's more resistant
to sheer stress.

Whilst most fluids change
viscosity with temperature,

non-Newtonian fluids,
like this cornstarch, water mix,

are also altered by force.

The larger the force he applies,
the thicker it gets,

and vice versa.

The fluid friction
of high viscosity liquids is

part of why they tend to be stickier.

Now, from sticky to tricky,
it's time for your test.

Question one:
If a substance has a higher viscosity,

does it take a larger
or smaller force to deform it?

[woman]
I'm stuck in mud here.

[Dallas] Yeah, that's
because mud is highly viscous.

[woman off-screen]
Can you move?

[Dallas]
Let's see.

-Yes... yes, she can.
-[woman laughs]

But I'm afraid the more viscous
the substance,

the more it resists
deformation by force,

so she had to yank hard
to release her left foot,

but she couldn't free the right one.

The rescue team is here,

and have deemed her a lost cause.

And now question two:
How does cooling effect viscosity?

Bitumen is a liquid that binds asphalt.

It's gooey and moldable when hot,

but if you've forgotten your
steamroller,

you might need to improvise,

because as it cools,
it can thicken to be

over 10 billion times
more viscous than water.

That's done it.

Right, question three.

A corn starch and water mix is
a sheer thickening, non-Newtonian fluid,

but can you guess how increased force
affects a sheer thinning fluid?

[man off-screen] Set... go!

[Dallas] The whole family is here
to demonstrate, apart from Dad...

[man off-screen]
Go, Sunni!

[Dallas]
...because he knows it's quicksand.

[tape rewinding]

The more force our family applies
to the sheer thinning quicksand,

the less viscous it becomes,

so the more easily
it deforms and they sink.

[man off-screen]
That's good.

[Dallas] Great work, Dad.

Now, keys are in the ignition,
flight's booked.

Go, go, go. Go now.

[glass shatters]

[electricity crackles]

[Dallas] One thing I rarely
find myself contemplating is popping

an object on a friend's head
and then attempting to boot it off.

It's just that the results tend to be,
well, a mixed bag.

It can be outrageous,

but more often... atrocious.

He was lucky, three inches lower
and that would have been even worse.

Faces have feelings, do not use them
as plinths for target practice.

Best to leave that to the experts,
like this one.

Our kicker swings her upper leg,
generating plenty of momentum,

whilst maintaining sufficient
contact force and friction

between her supporting foot
and the ground.

As her knee lines up with the target,
she follows with her foot

and connects just before
fully extending the leg.

This whole process maximizes force
without sacrificing stability.

So the key lies in generating
lots of force with a kick

to spectacularly launch the object,

but not so much momentum
that you spectacularly launch yourself.

It can take years
of dedicated training to master.

But who's got time for all that?

This lady is starting out by aiming
at an imaginary object

above her friend's head,
that seems safer.

[woman]
Okay, ready?

-[woman yelps]
-[laughter]

[Dallas]
But it's not.

Excessive vertical momentum
with the entire kicking leg

reduced the contact force between
her supporting foot and the ground.

Oh, plus, socks on a shiny floor...

-[woman yelps]
-[laughter]

...not great for friction.

Okay, let's introduce
an object... but what?

[man] Ready?
Okay, you ready?

[man off-screen]
I don't know these guys!

-[Dallas] Oh, for goodness sake.
-[man off-screen] Go, go, go, go.

[laughter]

[Dallas] Yes, very good.

[man] Okay?

[Dallas] Again, we observe lots
of vertical momentum with one foot,

not a lot of contact force
from the other,

plus, rubbish aim.

Also, I wouldn't have
gone for pineapple,

maybe something softer but not those.

[laughter]

This party ninja is aiming
for her friend's cap,

but the friend is somewhat taller.

How will this work?

[laughter]

[Dallas]
Not very well.

To reach the cap, she generated
an extraordinary large upwards momentum

reducing the contact force
and friction with the floor.

-[laughter]
-Again, this is dangerous.

Please do not do it.

[electricity crackles]

[metal creaking]

When someone asked me
if I'd do an inversion on a pole,

I'll admit, I was a little confused,
but then I realized it was this.

♪ ♪

And I was merely concerned.

You see, it takes serious
skill and science to do

upside-down acrobatics on a pole.

This, for example, is an expert.

Now this is some bloke.

-[man grunts]
-[woman shrieks]

But don't worry mate,
it happens to the best of us.

[screams]

Yes, a pole inversion is
simply a peculiar-sounding name

to describe any number
of topsy-turvy moves you can do

on a fitness pole, and, as you've seen,

it's not easy, but, as always,
physics is here to help.

♪ ♪

As our dancer reaches the pole,

she swings upwards
and gains angular momentum,

getting her into a classic inversion.

She grips the pole tight
from either side,

because the greater the force applied,
the greater the friction.

And finally, by keeping her center
of mass close to the pole,

she reduces the turning effect
rotating her down.

So, we are going big
on frictional force here,

but before that we need to get inverted
with a little bit of momentum.

[man grunts]

Yes, it's very good,
but it's not exactly inverted, is it?

[man grunts]

Well, that was inverted.

He had lots of momentum, but the only
real force applied was to his face.

[man] Aah!

[Dallas] That's better.

Now, how about a classic shoulder mount?

♪ ♪

[pole squeaking]

[woman shrieks]

[Dallas]
Okay, let's work on the friction.

Yes, rubbing away sweat helps increase
the coefficient of friction.

[pole squeaks]

[Dallas] Yeah, I reckon
a couple more rubs next time.

A different approach now.

Gripping with legs means
she can potentially apply

more force to the pole.

[woman shrieks]

Letting go means she can apply
more force to her face.

She moves her center of mass
away from the pole,

but keeps a firm grip with her legs

until she loosens that grip,
thereby reducing friction.

[woman shrieks]

How are you feeling?

[woman]
I'm good, yes.

[Dallas] Great because once
you nail the science...

this is said to be healthy
for body and mind.

-[laughter]
-[man off-screen] Oh!

Although I prefer Sudoku.

[glass shatters]

[electricity crackles]

As we reach the end of another
saunter down Stupid Street,

I'll remind you not to attempt
any of the stunts you've just seen.

Famous rocket scientist
Wernher von Braun once noted,

"Research is what I'm doing
when I don't know what I'm doing."

It turns out, he wasn't the only one.

[boy] Aah!

♪ ♪

[Mittens meows]

[woman laughs]

[man off-screen] Get him, Greg!

[woman off-screen] I'm good.