06x16 - Hurricanes, Half Pipe and Skiing

[bunniefuu]

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

Yes, this is the show where we
merge intelligence with idiocy

in a cornucopia of carnage.

As our trusty team of testers explore
key scientific principles

so you don't have to.

Then we explain what
went wrong and why.

With their assistance,

we'll scrutinize the science
behind Aeolian regimes,

angular approach and the
perils of reaction force.

So don't try any
of this at home.

Actually, don't
try any of it at all.

Watch out, it's the
Science of Stupid.

In this show we'll
be looking at

dynamic friction.

The results of the
Coriolis force.

And lateral forces.

But first this.

Did you know, we may have flat seas

to thank for the invention of
skateboarding?

Back in the 1950s,
Californian surfers,

frustrated by the lack of waves,
stuck wheels onto boards.


off properly

and a group of teenagers in the

Arizona desert started
using water pipes for tricks.

And thus the
half-pipe was born.

Things have really
taken off since then.

The half-pipe has evolved
into a sport in its own right.

It's no longer the sole
realm of the skateboarder.

Anyone with a set of wheels and nerves
of steel can get in on the action.

But it's harder than it looks.

Scientifically speaking, the half-pipe
is a pair of brachistochrone curves,

a bit like a pipe cut in half
longitudinally,

sometimes with an added elongated

flat central section.

There aren't many skaters who could tell
you that, but there's a lot of fewer

scientists who
can land a McTwist.

Descending the ramp, his gravitational
potential energy is converted into

kinetic energy and he speeds up.

His momentum keeps him going to ascend
the opposite ramp

and repeat the process.

If he can build enough speed, adding
energy by pumping with his legs,

then the steeply angled ramp will launch
him into a vertical trajectory to help

him catch some air.

Aided by the steepening inclined
planes of the half-pipe,

riders can achieve speeds that can
launch them over two meters

above the top of the ramp.

This allows for some spectacular aerial
acrobatics, which sounds fun.

Old-school.

Looks like he's gone back to the
grassroots of the half-pipe.

And now he's back to
the roots of that grass.

The shallow angle of the ramp results in
a shallow launch trajectory.

And with insufficient velocity he tries
to bail out,

proving old-school isn't always cool.

At last, a use for
the micro-scooter.

[man] Ugh.

[Dallas, off-screen] That doesn't
involve annoying pedestrians.

This guy launches himself into a steep
trajectory that allows plenty of airtime

for his trick, but catches himself
awkwardly and lands on his feet,

where friction slows him quicker than
the scooter would have, which means.

[man] Ugh.

[Dallas, off-screen] It's
not really his day today.

This guy seems to have
remembered his science.

Gravitational potential energy, kinetic
energy and momentum.

If only he'd
remembered his helmet.

As he shifts his weight forward to
prepare for the up-ramp,

he twists the board so the wheels are no
longer aligned with his momentum,

and friction decelerates
the board, but not him.

He'll have to face it,
that didn't go well.

So that's half-pipes,
a lot of fun.

[man] Ow.

[Dallas, off-screen]
Unless that happens.

[man] ******* hell.

[Dallas] You have to be a really serious
weather disaster to warrant getting

your own name.

Hurricanes have this dubious honor and
it's hardly a surprise.

A larger hurricane can expend the energy
of 10,000 atomic bombs.

That's because a Category 5 hurricane
has to have wind speeds in excess of


tornadoes they stick around.

The longest, Typhoon John,
lasted for 31 days.

And covered over 8,200 miles.

I wonder how far
this toilet will get.

Whether you call them cyclones,
typhoons or hurricanes,

they are deadly and destructive,
giant, spiraling,

tropical storms that build power over
oceans

before unleashing vast quantities of

wind and rain as
they make landfall.

But how do they form?

Hurricanes begin in warm
oceans where water evaporates.

When this water reaches a certain
height,

it condenses and forms thunderclouds.

These clouds are affected by the
large-scale circulation

of winds around the globe, which,

thanks to the Coriolis force,
spins them into a spiral shape.

As it grows, a tropical disturbance
becomes a tropical depression,

then a tropical storm
and then a hurricane.

When they make landfall, the intense
winds and rain can bring about flooding,

structural damage
and storm surges.

Some hurricanes can release more than


That's enough for every person on earth
to take about 20 showers each.

So if you hear a hurricane warning
you're best to take cover where you are,

because driving home

could prove to
be a costly mistake.

Wind battering the tops of trees applies
a turning force they may not have the

material strength to withstand.

This city in Russia is well known for
its space industry,

so you'd imagine it would be

well-made.

But you'd be wrong.

The fence has a large surface area

and so experiences a large drag force
from those

hurricane-strength winds.

Yeah, I think you're gonna
have to go the other way.

So that's hurricanes and storms for you,
extreme weather that can cause extreme

damage and a lot of mess.

[woman] Holy ****!

[Dallas, off-screen] Honestly, it's not
worth tidying your lawn

until the storm's passed,

I promise.

♪ ♪

Some people seem destined to learn their
physics the hard way,

but what principle will these guys
demonstrate in the process?

[man] Okay.

[Dallas, off-screen]
Did you guess what science

these pool roof jumpers
are about to show us?

[man] Okay.

[beep] [beep] [beep]

[Dallas, off-screen]
It's material strength.

Most of this roofing is corrugated
iron and fairly solid.

But that bit is a plastic
window, which is brittle.

In other words, it doesn't have the
sheer strength

to withstand the force caused by

his weight.

[man, off-screen]
[beep] [beep] [beep]

[Dallas, off-screen] Luckily there was a
handy pile

of boxes there to break his fall.

[man] Are you OK? Are you OK?

Bud, are you hurt?

[Dallas, off-screen] It's a valuable
lesson on why roofs and pools don't mix.

I think that skiing is probably
hard enough without adding

any obstacles to negotiate.

But many skiers aren't as zen as me

and they just got fed up with being
upstaged by their

flashier snowboarding
counterparts.

And so free-skiing came to be

and one of the most popular features is
the box-rail.

When you get the hang of it you can pull
off some serious stunts.

But before attempting anything at those
speeds,

you'll need to practice your balance,

coordination and timing before heading
out on the snow and ice

to make a complete
fool of yourself.

Despite being a simple box with a
plastic top and metal edges,

the box-rail is obviously capable of
seriously, not to mention painfully

tripping you up.

So with that in mind, let's get some
advice about skiing on a box-rail.

Gravity accelerates our man down the
snow slope providing forward momentum.

To mount the box-rail, he must generate
vertical velocity by hopping up.

Once sliding on the rail, his forward
momentum

is usually enough to overcome the low

coefficient of dynamic friction between
the box and his skis.

The wide flat surface allows some room
for error and sideways movement.

But as always, if your center of mass
strays too far to one side

you'll lose your base of support

and fall from the rail.

[man] Argh.

[Dallas] This all looks a bit risky to
me,

so I've enlisted the help of our team of

researchers to see how they cope with
the dangerous combination of

forward momentum, vertical velocity
and dynamic friction.

Let's see if a
small slope is helpful.

Not in this case.

Our researcher has forgotten that the
box offers slightly

more dynamic friction than the

snow on the approach slope.

His skis decelerate quicker than his
body and he leaves them behind.

Back to the drawing board.

Let's try a larger slope
and see how that works out.

[man] Oh my God!

[Dallas, off-screen]
Yeah that's worse.

He fails to get the right combination of
forward momentum and vertical velocity

to make it onto the box-rail, and his
footwear catches the edge.

We had to give this
researcher the boot.

[man] Oh my God!

[Dallas, off-screen]
And here is his replacement.

Not exactly a good
first day in the office.

This skier rotates his ski sideways,

lowing dynamic friction and making for
easy

sliding both along the rail and off it.

After that he wouldn't
put his skis back on.

Which didn't make any
discernible difference.

The more observant amongst you

might have guessed that we have come to
that point in the

show where we sit down, concentrate

and really focus on one particular
principle.

It's what we like to call the science
lesson, so who can tell me what

links the following?

This kettle-wielding
cloud maker.

These amateur alchemists.

[man] What the ****!

Blow it out, blow it out!

Your hand, blow
it off your hand.

[Dallas, off-screen]
And this cold weather surfer.

[man] How's the
conditions today?

[man] I can't hear you?

[Dallas] Alright, hands down.

They are all examples
of phase changes.

"What's a phase change?"

I hear you cry.

Well, phase changes are a substance's
transition between the states of

a solid, liquid, and gas.

They occur as molecules change

how much kinetic energy they have and
how much they

vibrate, causing intermolecular bonds
to be made and broken.

When this dry ice frozen carbon dioxide
encounters the warmer water,

its molecules gain kinetic energy and
start vibrating more violently,

breaking bonds between molecules

and causing it to sublime from a solid
straight

into a gas, whose
molecules are free to move.

Super-cool sodium acetate
liquid will do the opposite.

Given to something to nucleate on,

solid crystals form the liquid as its
molecules lose

kinetic energy and bond
into a regular structure.

And the more surface area available,
the faster they grow.

Right, let's see who's been paying
attention with a little pop quiz.

Question one.

What is a phase change?

Well, she looks a little
tongue-tied so I'll tell you.

It's the transition of a
substance between states.

In this case, the liquid
saliva on her tongue into ice.

Don't worry though, all it needs is some
warm water to break those

intermolecular bonds.

Simple.

Okay, question two.

What happens to something
when it's given more energy?

That's right, it will melt,
sublime or in this case.

[man, off-screen] Slow.

[man] Real, real slow.

[Dallas, off-screen] Vaporize.

[man] Oh ****!

[Dallas, off-screen] The water molecules
in the turkey

suddenly get more kinetic energy

as they're dropped into the boiling oil,

allowing those intermolecular
bonds to break and the water

to become steam.

[man] That's not
how you wanna do it!

[Dallas, off-screen]
Here's another example.

These coins are warmer than the dry ice
so it's subliming where they touch,

going straight from a solid to
a gas and making them dance.

Last and final question,
and this one is quite tricky.

What can make a
material freeze quickly?

[man] We are going to test
to see what happens when...

...you throw a pot of
boiling water into the air.

[Dallas, off-screen] I can just tell

this is gonna be one of those
experiments you shouldn't

try at home.

Yep, I was right.

[man] Yep...

...that's pretty cold.

[Dallas, off-screen] But I think the
answer we were searching for

was surface area.

Throwing water into the air creates tiny
droplets,

each with a lot of surface area

exposed to the cold air,

making them freeze instantly
into tiny ice particles.

It's a neat trick.

As long as you keep
hold of the pan.

[Dallas] Prepare yourself
for something rather special.

It's softer on the knees.

Retro running, or running backwards to
the uninitiated,

is gaining in popularity.

Maybe it's because it burns more
calories than running forwards.

And it's fun.

Well, most of the time.

Running is something that millions of
years of evolution has shaped us to do.

With our upright posture and ability to
shed heat through sweat,

there are few mammals that can beat a
human over long distances.

We are literally built
to run, but only forwards.

Going backwards is
more of a challenge.

As our man runs backwards,

he takes short, rapid strides and keeps
his body upright,

but it's hard for him to extend his base
of support underneath his center of mass

in order to maintain
dynamic stability.

A limited field of vision makes it hard
to spot obstacles so he needs to take

quick glances in order to bring the
direction of travel

into his field of vision,

to build spatial memory
of where he's about to go.

So to break that down,
there are two major issues.

One, you can't see
where you're going,

and two, we're not
designed to run backwards.

But according to its advocates, retro
running improves neuromuscular

efficiency so we sent our
researchers to give it a go.

And what better way to
start than with a race?

Play this clip backwards and it looks
like a very close race.

Doesn't work
forwards, mind you.

This guy's knees and ankles

can't bend enough to extend his legs
backwards to maintain

dynamic stability.

So that commanding lead is a
bit spoiled by that roly-poly.

But you don't need to race to feel the
health benefits of retro running.

You can incorporate it
into all sorts of exercise.

But you probably shouldn't.

Spatial memory only works when objects
stay where you expect them to be.

Or your workout could end

with you aching in
some unexpected places.

So, should you find yourself walking
backwards,

remember about spatial memory.

And poetic justice.

This would be ladies' man had been
facing the direction of travel,

so had the chance to build
up a mental map of obstacles.

But a pretty face
turned his head.

And hurt his derriere.

Nobody likes digging out snow,

which is hardly surprising when you
discover that a

single shovelful can weigh more than 20
pounds.

Even small scoops
can leave you chilly.

It's no easier if your best
friend lends a helping hand.

[man, off-screen]
She got the shovel.

[Dallas, off-screen] So maybe these
workmen have the best idea.

It does look fun, but that
snow's not gonna clear itself.

Before we can answer, "What's
the best way to shovel snow?"

we need to know a
bit more about snow.

Powdery snow is relatively grippy,

in part because it's deformable so it
shapes to the

tread of his shoes and in
part because it's quite dry.

But this powder snow can be compressed
into almost ice,

either by compaction or as

part of the melting process.

This ice-like snow is much more slippery

because it won't easily deform around
the tread

of our man's shoes.

It's also wetter, with a lower
coefficient of friction, which he.

[man] Argh.

[Dallas, off-screen]
Needs to watch out for.

Of course, you can always maximize your
chances of getting back in the house

unbruised by having
the right equipment.

Good boots provide good traction

and a long-handled shovel will mean
you'll bend over

less, making it easier to balance as
long as you don't overload it.

Right, let's see how
our experimenters get on.

Well, it's a good
shovel but those boots.

[screams]

[Dallas, off-screen]
Don't look grippy enough.

Here, the compressed snow has become
ice-like, which has very low friction.

Meaning that drive is gonna
take a bit longer to clear.

Of course, if you snow has melted and
refrozen on your roof

then that low friction

can be even more of a problem.

[man] You're going down.

[man, off-screen]
Just go under it!

[laughs]

[Dallas, off-screen] Lateral force from
his weight

on the slope of that roof overcame

what friction he had.

But at least he had some easily
deformable,

uncompressed snow to land on.

This man looks like an expert.

Highly grippy boots and a long-handled
shovel to minimize bending.

But there's one thing
he hasn't considered.

Wind.

Stephen Hawking, the late theoretical
physicist, cosmologist and all-round

brain box once said, "Science is not
only a disciple of reason

but also one of
romance and passion."

He was talking about space exploration
but he could just as well have been

talking about this lot.

♪ ♪

[man, off-screen] That's
not how you want to do it.