07x07 - Snowmobiles, Bicycles and Fires

[bunniefuu]

[Dallas Campbell]
This is the Science of Stupid.

[electricity crackling]

[klaxon blaring]

Yes, this is the show
where the rock of science

meets the hard place of stupidity.

-We examine the misguided mischief...
-[screams]

...of amateur analysts while they
struggle with scientific principles.

-[screams]
-[laughter]

-We'll reveal what went wrong...
-[man off screen] Whoa!

[Dallas]
...and why.

Maybe they don't get angular momentum,

the magnitude of the Magnus effect,
nor inverted pendulum,

but we do, so don't try
any of this yourself.

Watch out, it's the Science of Stupid.

[electricity crackles]

In this show, we'll explore

the fiery intensity of flash points,

the worst way to get off
the roof of a car,

and the science behind nodding off.

Oh, come on, come on.
Do it, do it, do it, do it. Yes.

But first this.

-[glass shatters]
-[electricity crackles]

[glass shatters]

We've always had great fun with snow,

on this show there have been some
wince-inducing moments, for sure.

But I am confident today
will be absolutely pain-free

as we explore the science behind
people on snowmobiles,

launching themselves off ridges.

In the hands of the pros,
it's a thing of grace and beauty,

of course in the hands
of amateurs, it's not.

[man] Aah!

[Dallas] With a bit of practice
these guys can pull off

huge jumps and amazing stunts.

That... wasn't one of them,

but trust me, they can,
so, stay alert and look out for trees,

particularly ones that fight back.

It looks quite simple--
aim a snowmobile at a steep slope

and hang on for dear life.

But I bet there's some
complicated science to be aware of

if you don't want to spend your
après-ski in the emergency room.

Our man must choose
the right ridge to jump off.

If he accelerates too hard
off a steep ridge,

his angular velocity could cause him
to over-rotate backwards.

But if the ridge is uneven,
he might gain angular velocity

that causes him to roll.

And, as with any type of jump,

our man must also choose
the landing spot carefully.

That bit really is quite important.

Having briefed some of our
more expendable researchers,

I then sent them out
and wished them luck.

They should be okay if they remember
to pick an even ridge,

accelerate correctly,
and try to land the right way up.

Here's Barry from the post room.

He didn't seem keen,
but he is doing great.

Oh, Barry.

[screams]

Barry's uneven launch
gives him angular velocity,

causing his snowmobile to roll...

which means he'll be doing a bit of
overtime to pay for those damages.

Shivanni here from marketing, and she's
found something a bit less steep.

[screams]

But the results are fairly similar.

Shivanni applies too much throttle,
which leads to too much acceleration

creating too much angular velocity...

[screams]

...which all leads to a chilly bottom.

[laughter]

Ah, now here's Mike,
our visionary CEO.

-Good jump...
-[man off screen] Aah! Whoa!

[Dallas]
...but he didn't see that coming.

Mike has the correct amount
of acceleration

and a good, smooth ridge to jump over,

but he forgot what we said about
checking the landing area

being clear of obstacles.

[man off screen] Whoa!

-[man off screen] Oh my God!
-[man 2] Are you all right?

[Dallas] Shame,
we always looked up to Mike.

[electricity crackles]

[creaks, clatters]

Today we are looking at
the least demanding activity

we've ever covered on the show,

it also happens to be
one of my favorite pastimes.

So stay alert and try not to nod off...

as doing so can be embarrassing...

and quite painful.

I am exhausted just watching that,

in fact, I might have a power nap.

Apparently the correct term for a
doze lasting up to 30 seconds

is a micro-sleep.

I can just about squeeze one in

while you learn about
the science of nodding off.

When people enter sleep,
their body and muscles relax.

Keeping your head up requires
engaged muscles.

So while a person sleeps, the head
starts to fall under its own weight.

The movement is sudden,
so it wakes the person up,

they reengage their muscles
to reposition their head,

they drift asleep again
and the cycle repeats itself.

[snores]

[yawns]

Excuse me. That's better.

Any parent will tell you kids
need more sleep than adults.

If they're made to keep
to an adult's timetable,

they can easily become sleep-deprived.

♪ ♪

But one thing this kid
won't be deprived of is ice cream.

As he falls asleep,
his neck muscles relax,

which causes his head to fall,
waking him up, and for a few moments,

he's just about conscious enough to eat
before falling asleep again.

This little fella, just like all of us,

will spend a third of his life asleep,
approximately 25 years,

but he's not letting it
get in the way of snack time.

Do be careful,
this can be a choking hazard.

[snoring]

I once visited the call center
at my bank,

and she looks vaguely familiar.

[snoring]

Yeah, I knew I recognized her.

There are five distinct stages of sleep:

the first has you transition
from consciousness to light sleep,

like that.

Yeah, that's fixed it, nobody, nobody
will notice that at all, it's fine.

Monks are renowned
for mastering their physical bodies

to achieve spiritual enlightenment,

but this little fella hasn't quite got
the hang of it just yet.

He's falling into micro-sleep,
three to 30 seconds of bliss,

during which external stimuli
are not perceived.

[boy] Ooh!

[Dallas] I'm exactly the same
when I meditate at home.

[snoring]

This chap looks like he's officiating
a swimming competition.

He'll need to keep
a sharper eye than that.

[snores]

[whispers] Come on, sleepyhead.

[snores]

Well, that's one way to freshen up.

As our official enters
a deeper sleep state,

his body and muscles relax, so his head
starts to fall under its own weight.

This pulls his center of mass
outside his base of support,

and he drops off...

the edge of the pool.

He'll be totally refreshed
when he finally surfaces.

[electricity crackles]

[metal creaks, clatters]

[Coach Salter] All right, guys, we're
here at Salty Dog Jiu Jitsu.

I'm Coach Salter.
We're working on our takedowns.

[Dallas] Can you guess
what science this wrestling class

will demonstrate with their takedowns?

[glass shattering]

[electricity crackles]

[Salter] All right, guys, we're here
at Salty Dog Jiu Jitsu.

I'm Coach Salter.
We're working on our takedowns.

[Dallas] Did you guess what science
Coach Salter's class

are about to show us?

[Salter] She shoots her double legs,
as long as she runs...

[Dallas]
No, not them. Them.

-[screams]
-Yes, that's right.

It's turning effect.

Our wrestler, let's call him Wrestler A,

grabs one of his opponent's
legs instead of both,

leaving Wrestler B
able to reposition himself

and apply a horizontal force
back at Wrestler A.

So when Wrestler A applies a horizontal
force near his opponent's waist,

Wrestler B provides an opposing
horizontal force on the floor...

[screams]

[tape rewinding, squealing]

-...creating a turning effect.
-[screams]

Easy as A, B, C.

[electricity crackles]

[whirring]

Centuries of wisdom and posing

have made yoga the perfect antidote

to the stresses and strains
of the modern world.

And to pass the baton of wisdom
onto you, my gentle viewers,

today we're looking
at one simple but surprisingly tricky

asana, or posture, called the crow pose.

Here is a crow, and here is a crow pose.

Get it? Crow.

-Crow pose.
-[woman] Aah!

[Dallas] Almost. Let's try again.

Crow, crow pose.

[man off screen] Do it, Derek.

[Dallas] Or broken nose?

The unofficial world record
for holding this pose is

just four minutes and 21 seconds,
which sounds beatable,

but if you want a world record,
you'll need to pay close attention

to the following science.

First she places her hands on the floor,

resting her knees
on the backs of her arms,

then leans so her
center of mass is over her hands,

which become her base of support,

enabling her to raise
her feet from the floor.

Muscles in the forearms
counter the turning effect produced

if her center of mass were to move
outside of her base of support,

and the mat helps by increasing
the frictions at her hands

so she doesn't slip.

Particularly handy
when pushing out in style.

So, it seems to be largely
about good balance,

but we wanted to check if there were
any underlying complications

and sent out our top
researchers to investigate.

Lovely tiger cushion,
powerful forearms, friction-y mat.

-[woman shouts]
-[glass clatters]

Yep, this mount wasn't very crow-like.

[laughs]

Her center of mass is too far forwards,
a turning force is generated,

and she pivots around
her wrists, falling forwards.

She tries to rescue some dignity
by converting the fall into a headstand.

-[woman shouts]
-[glass clatters]

[laughs]

Points for style though.

[laughs]

Let's see if this guy can do any better.

That's it, now lean forwards until
your center of mass is over your hands.

[man grunts]

No. That's not it, try again.

[man] Aah!

[Dallas]
No, that's more roly-poly.

Our yogi leans forward too quickly,
and his center of mass

ends up outside his base of support.

It's hard to achieve enlightenment
when you've got gravel down your shorts.

[bell rings]

-[clattering]
-[burbling]

Okay class, settle down, settle down.

Yes, it is time to galvanize
your gray matter and get ready

for today's science lesson,
the part of the show where we scrutinize

a specific scientific principle,
and, as always,

there'll be a quiz at the end,
so do try to concentrate.

Right, can you guess what today's
principle is from the following?

[man off screen] Yo, just do it.

[Dallas]
This careless c*ck drinker.

Don't try this at home.

[man off screen] Whoa!

[Dallas]
This terrible turkey technique.

Don't do this either.

And this birthday surprise.

-[woman] Woo!
-[girl shrieks]

[Dallas]
Happy birthday?

[woman]
It's okay.

[Dallas] If you said "flash point,"
get to the top of the class.

This is the critical temperature
above which the vapors

of a liquid fuel will combust.

Let's take a look at the science.

Below its flash point, there isn't
enough vapor for a liquid fuel

to combust in the presence of a flame.

But when the same fuel is heated
above a specific temperature,

there's more evaporation
and enough vapor to ignite.

That temperature is called
the flash point.

If the fuel is dispersed
into small droplets,

there's a higher surface area
available for evaporation,

and so the fuel can ignite
at a temperature below its flash point.

That was a demonstration conducted
under qualified safety guidance.

Please do not attempt to copy it.

Right, it is time for the quiz.

Question one:
What happens to a liquid fuel

when its temperature is
above its flash point?

This mechanic is trying to ignite
the fuel in the engine.

-[flames whoosh]
-Success!

Of course, if you do manage to set
something you didn't want to alight...

[flames whoosh]

...then job one should always be
removing the fuel source.

Okay, time for question two.

How can a fuel's vapors ignite

when its temperature is
below its flash point?

This experienced fire performer
might be able to work out the answer...

if he uses his head.

But not like that.

The fire-breather blows out
a mist of small droplets,

the droplets have a high
surface area for evaporation,

meaning plenty of vapor, so the kerosene
can ignite below its flash point.

Unfortunately, he walks
straight into his own fire.

But no worry, the strong community
spirit has everyone rushing to help.

And time for the last question:

Which element of a liquid fuel combusts
when it's above its flash point?

These researchers have
kindly agreed to look into it.

[man] Just light it on fire now. Go.

Do you want to stand back?

-[man 1] Aah!
-[man 2] Whoa!

[Dallas]
If you'd have listened to your friend,

you'd still have eyebrows.

The flash point of gasoline vapor is
minus 45 degrees Fahrenheit,

which is one of the reasons
it's so useful as a fuel.

It's easily combustible,
even in a chilly backyard.

I think it would be safer
just to phone for a pizza.

[man] Yes!

[laughs]

[glass shatters]

[electricity crackles]

[Dallas] Yesterday, I woke up
to find dents all over the roof

and hood of my car,
it really wasn't amusing.

When I told my dad, he said
there must be a goat in my garage.

I thought it was one of his silly,
old sayings, but it turns out...

[goat bleats]

They are surprisingly good
at clambering about on cars...

[bleats]

-...whereas most people... aren't.
-[man groans]

Using your car as some
kind of makeshift as*ault course

is quite evidently an appalling idea,

likely to end in a degree
of pain and discomfort,

and here's the science to show why.

When jumping onto the car,
our man needs to be aware

that there won't be much friction
between his shoes

and both the painted metal bodywork
or the glass of the windows,

which means he could easily slip.

If he jumps from the roof of the car
onto the sloping windscreen or hood,

the angle of the surface will reduce
the friction force,

making him more likely to slip.

If you ever feel the desire
to clamber over a car,

remember, most of the vehicle
will be rather slippy.

My advice would be don't do it,

particularly when it's
not even your car.

But no one ever listens
to little old me.

This really is a bad idea.

[man]
I feel like...

the world's mine.

[laughter]

[Dallas] Baby steps.
First the sidewalk, then the world.

[man] Aah!

[Dallas] He makes it up
onto the car without any issues,

but the slope of the hood
and low coefficient of friction

between it and his shoes means he slips.

The impetuousness of youth.

[laughter]

I wonder if it's any easier
to stay on a moving car.

[men grunting]

No, obviously not.

-[man] Ow!
-[car honks]

[Dallas] When the car accelerates,
there isn't enough friction

between their shorts and the trunk
to keep them accelerating with it.

But the higher coefficient of friction
between the sandal and the trunk

means that it remains
long after its owner departed.

So, unless you're a sandal,
don't try this at home.

[laughter]

Here are some of our researchers
on the way to the lab.

[horn honks]

Our researchers have learnt
that by walking across the hood,

instead of jumping onto it,

they would apply less force
and avoid slipping off.

It's a valuable lesson, and it looks
like the driver's also learnt something.

[electricity crackles]

[thudding]

BMX bikes have been around
longer than me,

so quite a while then.

I had one in the 1970s,
but all I remember is falling off it.

And as we approach 50 years
of the BMX, I thought we'd take a look

at one of the more unusual ways
people have found to use one.

♪ ♪

"Impressive," I hear you say,
"but why unusual?"

Well, if you look closely
no one is peddling,

but that's because this is a pump track.

It's probably best left to the pros,

-which... he isn't.
-[screams]

So how do people propel themselves
at great speed over multiple jumps

without the need to peddle?

Let's jump into the science.

A pump track features bumps
the rider must use to accelerate.

Going up a bump,
he compresses his legs

and brings his BMX up towards his body.

Coming down a slope,
he extends his legs,

pushing the bike downwards
and into the slope.

This is called pumping.

Some of the downwards force
he applies generates a forward force

in his direction of motion,

this gives him more momentum

than if he were accelerating
under gravity alone.

To generate the maximum
amount of momentum,

he must achieve the correct rhythm
of pumping between the bumps,

this means the bumps need
to be appropriately spaced.

So, it's all about compression,
momentum and rhythm,

and anyone who's ever
seen me on the dance floor

of course knows that I've got all three
in bucket loads, triple threat.

But let's see how this lot got on.

[announcer speaking indistinctly
over PA]

Of course you do need
to peddle to get started.

Oh, and they're off!

[bikers shout]

And now most of them are off.

Since there are so many riders
on this pump track,

it's important for them
to carefully time their trajectories.

However, as they accelerate
into the air,

one of them misjudges,
causing a mid-air collision.

[bikers shout]

[announcer on PA]
We've got a bunch of riders down.

[Dallas]
Yeah, I think we've worked that out,

but thanks for the confirmation
all the same.

[laughter]

Maybe it would be easier to just have
the track all to yourself.

Yeah, apparently not.

He doesn't land straight,
and so the impact force

rotates him into the ground,

resulting in a rapid loss
of his forward momentum.

[man off screen] You all right?

[Dallas]
Yeah, he's never better.

That is either a poorly spaced
pump track or a terrible ramp.

[laughter]

Or a catapult.

The kids built the bumps
too close together,

so there's no room to pump
down the side of the first bump,

and she crashes
straight into the second bump.

[laughter]

Oh, kids, eh, aren't they lovely?

[glass shatters]

[electricity crackles]

Science fiction writer
Douglas Adams once wrote,

"There is a theory which
states that if anyone discovers

"exactly what the universe is for
and why it is here,

"it will instantly disappear
and be replaced by something

"even more bizarre and inexplicable.

There's another theory which states
that this has already happened."

Judging by this lot, I'd say
that happened quite a while ago.

[man off screen] Whoa!

[woman screams]

[woman] Aah!

[laughs]

[man screams]

[man off screen] Whoa!

[man screams]