06x06 - Kayaks, Avalanches and Stunts

[bunniefuu]

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

Yes, this is the show that
squeezes the science

out of the stupid.

[laughter]

[Dallas off-screen] As our
band of reckless researchers

test the boundaries of
scientific knowledge.

[laughter]

So you don't have to.

Then we'll reveal what went wrong.
[man] Hiya!

[Dallas off-screen] And why,
demonstrating key principles

along the way.

Such as angle of reflection.

[grunts]

The amplitude of waves.

[screams]

And granular materials.

So, buckle up and hold on
tight because this is the

Science Of Stupid.

In this show we'll see how gravity
accelerates avalanches.

[man off-screen] Whoa!

[Dallas off-screen]
And skiers.

-[woman] You gotta let go of her.
-[Dallas off-screen] How friction

can aid
rope climbing.

As long as you know
what you're doing.

And how momentum
can make kayaking...

[screams]

Breathtaking.

But first, this.

Throw away your textbooks,
ditch your diagrams and

crumple up your calculus
because you can learn plenty

of science simply by heading
to your local playground

and spinning about.

[screams]

[Dallas off-screen] This
kid on a saddle spinner is

studying centrifugal force.

He'll go far.

[man] Oh no!

[Dallas off-screen] Whereas,
this boy is researching

something called
angular velocity.

[laughter]
[man off-screen] Incline!

[Dallas off-screen] I
wonder what he's learned.

Not much.

Yes, those playground spinners
are the ideal way to swot up

on some fascinating
scientific principles.

There's physics in the forces
that control your spin,

and biology too in what that
spinning does to your brain.

Here's how it all works.

[Dallas off-screen] On a
playground spinner you can

change your angular
velocity, or spin speed,

by altering your
moment of inertia.

Bring your limbs into
your body to speed up.

Spread them out to slow down.

Just don't let your center
of mass get too far from your

axis of rotation or
centrifugal force could

throw you out.

Furthermore, the act of
spinning moves the gooey fluid

in your inner ear, stimulating
tiny hair cells which tell

your brain you're moving.

Stop abruptly and the
fluid keeps moving,

so your brain thinks
you're still spinning.

That link between the ears and the brain
is the vestibular system.

It's there to
help you balance,

so please be kind to it with
a nice, controlled spin.

That is the exact opposite
of what I just said.

[laughter]

Tucked in tight, she has
a small moment of inertia

and a fast spin.

Until centrifugal force
pulls her into a classic

center-of-mass-outside-base
scenario.

[laughter]

Oh, for goodness' sake.

Where's an adult
when you need one?

Ah, here's one.

[girl off-screen]
Oh, Mum's going on.

[Dallas off-screen]
Understand the laws of physics.

[laughter]

And it's like you can
see into the future.

[woman] Please help me,
I'm going to fall.

[Dallas off-screen] But
before the inevitable,

some analysis.

Mass spread out, her moment
of inertia is quite large,

and she rotates slowly.
[grunts]

But here that mass is
unevenly distributed,

so her prophecy comes true.

[girl] Mum, are you okay?

[girl] Are you okay?

[Dallas off-screen] I
think she's been better.

[man] Li'l gonna
fall when he get up.

[Dallas off-screen] Ah,
this is a lovely scene,

a dad teaching his
son all about physics.

[man] He start
laughing real quick.

[Dallas off-screen] Well,
he seems to have mastered

moment of inertia.

Let's see how he does on
the vestibular system.

[laughter]

Yeah, not so good.

As he spins, so
does his ear fluid.

But when he stops,
the fluid keeps going.

And his brain and legs
just couldn't agree.

[laughter]

Learning science, more
fun than you think.

[man off-screen]
Look at him, he...

he can't get.

[Dallas] Question, what can accelerate
from naught to 80 miles an hour

in five seconds, feels like
being body slammed by a herd of

elephants and yet is as light
and soft and fluffy as snow?

[Dallas off-screen] Well, it
is snow, but not that snow.

That snow.

[man grunts]

Yes, we're looking
at snow avalanches,

or in other words, avalanches.

The biggest can equate to
about 100 Olympic-sized

swimming pools full of snow
chasing you down the slopes.

And this is how that starts.

[Dallas off-screen] When
a fresh layer of snow

accumulates on a mountainside,
a big enough disturbance can

allow its weight to overcome
frictional resistance.

This area is called
the starting zone.

As gravity pulls the
snow along its path,

its known as the avalanche
track, it gathers momentum.

The steeper the gradient, the
faster gravity can accelerate

the avalanche.

Until frictional resistance slows it
down in the runout zone.

Avalanches can be deadly,
and around 90% of avalanche

victims caused them
in the first place.

So, when you're
out on the slopes,

try to take a low
impact approach.

[Dallas off-screen] This
skier is hacking off a ridge

of snow for easy
access to the piste.

[man off-screen] Oh, oh my.

[Dallas off-screen] And now he's
triggered his very own avalanche.

[man] Holy moly!

[Dallas off-screen]
Holy moly, indeed.

The force of the falling
chunks helps the layer of snow

beneath overcome the
frictional resistance

holding it in place.

[man] I hope we're not going
to k*ll anybody on the trail.

[man] Me too!

[Dallas off-screen] Me three.

So, that's your starting zone,
and now gravity is hurtling

tons of snow down the avalanche track at
quite some pace.

So, one moment you're thinking
what a lovely day it is for a

ski, and the next
moment you're thinking,

'I wish I stayed in
the chalet hot tub.'

[man off-screen] Whoa! Oof!

Oof!

[Dallas off-screen]
Never mind.

Thanks to frictional
resistance,

that snow should slow down
somewhere in the runout zone.

But not always.

A dry avalanche is an
avalanche that kicks up a vast

envelope of light snow
called a powder cloud.

The cloud is made up of about


particles, but they can
reach astonishing speeds.

[speaking native language]

[Dallas off-screen] Here's a
powder cloud breezing through

Nagar Valley, Pakistan.

[man] The avalanche is very far.

[man] Let's leave, let's leave.

[man] It won't come this far...

...trust me.

[Dallas off-screen] I'm not
so sure because while it does

look fluffy and harmless.

[man] Get inside, quick.
[yelling]

[Dallas off-screen] These
clouds can travel at up to


potentially lethal blast

of pressurized air.

So, a few seconds later...

[speaking native language]

[Dallas off-screen] It
doesn't seem quite so fluffy

and harmless.

[shouting]

[Dallas off-screen] Oh,
there's the blast of air.

Do you mind
shutting the window?

It's suddenly
got a bit chilly.

This half-naked chap's about
to run his ATV off a cliff.

I don't know why, either.

But what scientific principle
is he about to demonstrate?

[Dallas off-screen] So, what type of
force will he show us as he waves

au revoir to his ATV?

[screaming]

And very nearly
two of his friends?

[laughter]

Well, it's torque, the rotational
equivalent of force.

The ATV's engine produces
torque in the wheel,

but that's not the problem.

Rather, it's the torque he
produces by pushing the ATV

from one side, so it rotates
slightly to the right and

applies a little
torque to this guy too.

[laughter]

I think he needs a
serious 'torque-ing' to.

Since its invention more
than 90,000 years ago,

the humble rope has been key
to some of civilization's

proudest achievements.

Agriculture, shipbuilding, constructing
the Great Pyramids of Giza,

but best of all, climbing.

[Dallas off-screen] Some
people are so good at rope

climbing, they can
even multitask.

Show-off.

Some people can take it
to a whole new level.

And some people...

[man] Ow!

[Dallas off-screen] Really
just shouldn't bother.

In the right hands, rope is
an ingenious climbing tool,

hundreds of fibers twisted
together to share the load.

And to climb one, you'll
need a fistful of force and a

foothold on friction.

[Dallas off-screen] The more
force he applies to the rope,

the greater the friction.

Since friction allows a force
at act perpendicular to a

surface, it's able to overcome the
downward force of his weight.

Using friction to wrap the
rope under one foot with the

underneath not only keeps it
taut but applies a tensile

force to lift him up.

That method of looping the
rope between the feet is known

as the Spanish wrap, but
there are all sorts of ways to

overcome the force
of your weight.

Here are some of my favorites.

[man] Oh my God.

[Dallas off-screen] Yes,
climbing the Trojan horse,

it's what you do at
festivals, apparently.

This guy's quite slight
and doesn't have a lot of

downwards weight to overcome.

But this is hard.

Let's see how a
bigger guy gets on.

[man] This is a
really bad idea.

[Dallas off-screen]
It's not that bad.

[man off-screen] Oh,
yeah, there we go.

[Dallas off-screen] The
wooden horse means another

surface for friction.

So, he can apply
force with his feet.

[cheering]

And with the admiration
of his people.

[groaning]

And then lose it again.

-[man off-screen] Oh, my God.
-[cheering]

[Dallas off-screen] Showing
off by pulling back too hard

also increases the force from his feet,
optimizing friction, but...

[grunts]

Well, let's just say they
don't build Trojan horses like

they used to.

[man] Yes!

-[Dallas off-screen] Yeah, very good.
-[man] Yes!

[Dallas off-screen] But this
is not so much climbing as

coordinated dangling.

[woman off-screen] Alright,
you've gotta let go of her.

[woman] Let your feet go first.

[laughing]

[Dallas off-screen] Actually,
let's just call it dangling.

On a horizontal rope, her
hanging weight is a big force.

-[man] Yeah!
-[cheering]

[Dallas off-screen] It's a shame it was
too much for her grip strength.

[woman off-screen] Alright,
you've gotta let go of her.

[woman] Let your feet go first.

[Dallas off-screen] But that lovely flip
really made up for it.

[laughing]

They're only laughing
out of a deep respect.

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

where we pick apart a particular
principle of science.

Tricky to say, trickier to
do, so pay attention because

today's lesson concerns a
form of energy that's been

responsible for a lot of pain
here on the Science Of Stupid.

See if you can
guess what it is.

[man off-screen]
Here comes the kick.

[Dallas off-screen] Any
moving object has it.

[man off-screen] Oh, my...

[Dallas off-screen]
It depends on mass.

[man] Is it alright?
Is the angle good?

[laughter]

[Dallas off-screen] But
even more so on velocity.

Got it yet? No?

[groaning]

[Dallas off-screen]
How about now?

[man off-screen] Oh, God.

[Dallas] Yep, we're
looking at kinetic energy,

the energy possessed by an
object due to its motion.

Like any other form of energy,
kinetic energy can't be

created or destroyed,
just passed on,

sometimes changing from one
type of energy to another

in the process.

For example...

[Dallas off-screen] Energy
must be transferred to an

object to accelerate it.

When it's moving,
that's kinetic energy.

Double its velocity and you
quadruple the kinetic energy.

But double the mass of an
object and you still double

the kinetic energy.

When it collides
with another object,

some kinetic energy is
transferred to the object to

move or deform it, and some
of it is converted into heat

energy and sound energy.

Okay, question one,
energy can't be created,

so how does an object
get kinetic energy?

[man] Yeah you got
it, yeah you got it.

[Dallas off-screen] Keep
your eye on the ball.

[man] Ready?

[man] Yeah.

[man] [Bleep], [bleep].

[Dallas off-screen]
That's right,

the energy must be
transferred to it.

Here, man transfers kinetic
energy into elastic band.

Band conserves it as elastic
potential energy then

transfers it back as
kinetic energy in the ball.

And since energy
is never lost,

the ball transfers kinetic
energy to his face.

[man] [bleep], [bleep].

[Dallas] Question two, the
amount of kinetic energy a

moving object has depends
partly on its mass,

but what else?

[woman] You're not
straight, mum.

[Dallas off-screen] This
professional performer and her

mum are going to help you out.

[woman] Right up to the sun, you've
gotta... legs apart.

Shuffle that way a bit more.
There, that's it.

[Dallas off-screen] Alright, bossy
boots, just get on with it.

Even a lightweight arrow will
have lots of kinetic energy

when it's fired at over


So, the answer is...

yeah, oh...

oh, well, it's velocity.

[woman] There you
go. Still alive.

[Dallas off-screen] Yes, but can you
still move from that fence?

[woman] Fine.

[Dallas] I'm just kidding, but
that was incredibly dangerous,

and she was an expert archer,
so please do not try anything

like it yourself.

Okay, question three, I think
we'd all agree that this

bouncy ball has a larger mass
than this ping pong ball,

but what hurts more?

[Dallas off-screen] This?

Or this?

[groans]

Well, there's lot
of variables here,

but the point is they're
not too dissimilar.

You see, whilst the bouncy
ball has more mass...

[groans]

The ping pong ball travels
about six times faster.

And don't forget, doubling
the velocity quadruples

the kinetic energy.

So, the speed's the thing
that makes it sting.

[Dallas] Now, I consider myself a
pretty flexible sort of chap,

but there's one yoga pose
that even I find tricky.

It's the scorpion.

[Dallas off-screen]
Balance upside down,

bringing your feet
right over your head.

They say yoga like this
prepares the body for absolute

stillness so the mind
can achieve perfect calm.

[woman] Ow.

[Dallas off-screen]
Yeah, I'm not so sure.

-[Lydia] Hey.
-[man off-screen] You alright, Lydia?

[Dallas off-screen] Don't worry, Dad,

-patio's absolutely fine.
-[man] Are you okay?

[Dallas] Perfecting any pose
named after a venomous animal

is always going to involve
a degree of discomfort,

but perhaps less if you
understand the science.

[Dallas off-screen] To
achieve a stable inverted

position, you need just enough
strength and momentum to bring

your center of mass
directly over your hands.

To position your feet over
your head whilst keeping your

center of mass aligned,
you need to achieve lumbar

extension, fully extending the
joints between vertebral discs

in the lower spine known
as the lumbar curve.

It's also important to
maintain good body tension,

or the wrong parts might
flex, and you may hit the deck

rather quickly.

So, momentum, body tension,
lumbar extension and,

of course, our old
friend center of mass.

How on earth are you supposed
to be at one with yourself

with all that going on?

Well, let's just start
simply with momentum.

[Dallas off-screen]
Not quite enough there.

This time surely.

Come on, here we go.

Don't look at me.

Focus on getting
enough momentum.

Yes.

No.

Um, but that was enough.

Here, momentum brings her
briefly to a nice center of

mass over base position.

Here, lack of body
tension results in a

kind of half-scorpion.

And just here I start to
wonder if that coffee table

really does go
with that cupboard.

I just think it's too pale.

I don't think drinking
is gonna help.

But that's a nicely
flexed lumbar,

a low and stable
center of mass,

and now for a
refreshing taste.

Of yoga mat.

[woman] Ow.

[Dallas off-screen] When her
center of mass shifted too far

over, she became less of a
scorpion, more of a bridge.

Anyone know how to remove
a straw from a nose?

[woman] Ow. Oh.

[Dallas off-screen]
Ah, good feng shui here.

Minimal décor, scented candle.

But, oh, hang on, there
shouldn't be a screen in that

money corner.

Yeah, that's much better.

For the most part, kayaking
or canoeing a river is a

relaxing, carefree pastime.

Paddle your way over
a waterfall, however,

and you're less likely to
watch the world drift by than

to see your life flash
before your eyes.

[man] Woo!

[screams]

[man off-screen] He's all hurt.
Oh, my God.

[Dallas off-screen] Don't
worry, he was okay eventually.

That was a 40 foot drop, but the
highest waterfall ever kayaked

is the 186 foot Palouse
Falls in Washington state,

over four and a
half times as high.

But paddling over any
waterfall is a bad idea,

and that's largely
down to momentum.

[Dallas off-screen] As our kayak
plummets over a waterfall,

it builds momentum.

Landing roughly nose down
helps reduce drag from the

water, so momentum is lost
over a longer period of time

and impact force is minimized.

A flat landing, however, and
an excess of drag can cause

momentum to be
lost too quickly,

resulting in rapid deceleration and an
unpleasant landing.

So, with all that momentum,
the last thing you'd want is

to hit a rocky outcrop,
enter the water laterally or

experience excessive
drag and impact.

But getting all three at once?

Now, that really
would be unlucky.

[grunts]

[Dallas off-screen]
Now, let's see.

Rocky outcrop, check.

[grunts]
Lateral entry, check.

Excessive drag
and impact, check.

Yeah, he was unlucky.

But will going backwards give
this guy a lower drag entry?

[man] Woo!

[Dallas off-screen]
No. Why would it?

[sighs]

In fact, by showing
off with a somersault,

he presented the water with
perhaps the least low drag

approach possible and then
struggled with buoyant force.

[sighs]

[chanting]

These two have heeded
my advice and have

no intention of attempting
to go down a waterfall.

They're going down a
beaver dam instead.

[man] Aww!

[Dallas off-screen] Branches
are more resistant to movement

of the boat than water.

[man off-screen]
You hit the rock.

Why didn't you guys
go to the middle?

[Dallas off-screen] But
that's a nice head-on,

low drag entry.

[man] "We're not going
to get wet," he says!

[Dallas off-screen]
And he was right.

Only you got wet.

I believe it was Isaac Newton
who warned us that every

action has an equal
and opposite reaction.

And if that action
is wanton stupidity,

then the reaction will
be a whole load of pain.

Like this.

[woman] Help her.

[man off-screen]
He... he can't get.