07x03 - Snow, Velodromes and Powerlines

[bunniefuu]

[Dallas Campbell]
This is the Science of Stupid.

[klaxon blaring]

[man] Whoa.

[Dallas] Yes, this is the show
where science meets stupidity.

[woman shrieks]

Standby to honor
the world's top amateur scientists

as they test the laws of physics

and fall foul of the consequences.

[woman screams]

We'll analyze their errors

to reveal what went wrong

and why

with the aid of science's
least forgiving principles.

[man screams]

Such as impact force...

thermal expansion...

and not forgetting flexural strength.

Take science for a fool
and the joke's on you.

Look out!

It's the Science of Stupid.

[electricity crackling]

In this episode,

we'll be exploring
the always surprising...

angular velocity...

the benefits of partial vacuums...

and we'll be shedding
a little light on voltage.

Okay, a lot of light, but first this.

[glass shatters]

[electricity crackling]

[glass shatters]

Picture if you will
a brisk winter's morning,

you peek through the curtains
and see the world

hidden beneath a blanket
of crisp, white snow.

It's truly magical.

Until you get in your car.

[horn honking, tires squealing]

Then, it's just unbelievably dangerous.

The big problems
with driving on snow are momentum

and a low coefficient of friction,

which is not helped
by a weird layer of water molecules

known as a quasi-liquid.

Here's the science.

Snow's consistency means it easily fills

in a tire's otherwise grippy tread.

Worse still, it's covered
by a film of water

in a quasi-liquid state,

not quite liquid, not quite solid

but very slippy.

The resulting low coefficient
of friction can cause a skid,

especially on a bend...

[tires squealing]

...where the vehicle's sideways momentum

easily overcomes
the back wheel's poor traction

with the ground.

The coefficient of friction is a measure
of the amount of friction

between two surfaces.

For instance, tires on tarmac on a dry
summer's day measures around 0.7,

but that can drop to around 0.3,
about half as grippy,

on a snowy street in Siberia.

Like this morning in Vladivostok

where everyone is stuck in the snow...

apart from him.

[car alarms blaring]

Coming through, yep.

Don't, don't mind me.

He's using the combination
of quasi liquid,

clogging snow, and steep gradient

to demonstrate transfer of momentum.

Mini bus transfers momentum to 4x4...

[car alarms blaring]

...to tractor...



tractor back to minibus,

and very nearly to this man.

Siberia, it's way more fun than you
think.

[people speaking in foreign language]

This young researcher, hi,

maintains traction and control
by easing around the corner.

Fast forward a few minutes and...

[tires squealing]

[crashes]

He does the complete opposite.

By increasing velocity
and therefore momentum,

he lost traction,

so whilst he wanted
to travel around the corner

his back end wanted
to travel into the fence.

[crashes]

But velocity isn't the only thing
that affects momentum.

There's also mass.

[horn honking]

[car alarm blaring]

One car in the car park
and you manage to hit it,

that's actually quite impressive.

[electricity crackling]

[creaking, clanging]

Do you like cycling really fast

but tire of having to slow down
at every corner?

Well, there's a special
magical place just for you.

Behold the velodrome,
where specially banked bends

help cyclists keep their speed
up to the max.

It's the domain of the crème de la
crème.

Cheer up, mate. There's no point
in crying over spilt crème.

So how do a velodrome's
banked corners help you go faster

and what problems lie therein?

Well, let's consult
our old friend, the science.

On a regular corner,
our cyclist is pulled inwards

by centripetal force

and outwards by centrifugal force.

[man yells]

But on a bank turn,
additional centripetal force

pushes the rider inwards

helping him build velocity
without falling off.

Cyclists tend to group along the
shortest route around the oval track,

exploiting the reduced air resistance
in each other's slipstream.

But get too close

and one wheel can transfer
momentum to another,

resulting in linear velocity

becoming angular velocity.

[man] Oh!

[Dallas] The banking in turns
is called super elevation,

and they can help you reach
extremely high speeds.

For example, on an Olympic-sized track

with no banking,
the maximum speed you could corner

without hitting the deck
is around 28 miles an hour.

But on a super elevation, you can fly
at up to 50 miles an hour.

[bell ringing]

[crowd] Oh!

[men grunting]

[Dallas] And then hit the deck.

Having built velocity around the turn,

the chap on the inside
fancied overtaking the leader

but didn't notice the guy on his right,

resulting in a bit of momentum transfer

and some angular velocity here...

and here.

[men grunting]

On super elevations, the angled bend
actually guides you round,

so you don't even have to steer...

[crowd] Oh!

[Dallas] ...except when someone
gets in your way.

Thinking about those bank tracks,
they do make lovely slides,

resulting in this chap's linear velocity

becoming angular.

[men, off-screen] Oh my God!

[Dallas] I know, it's a lot
of science to take in.

Here we are saving energy
in the slipstream,

looking for a gap.

There's one.

The initial cause was concealed
by the bottom in front,

but it's fair to say that this errant
leg

made the rider behind go
from linear to angular...

leaving an absolute mess
on the side of the track.

[electricity crackling]

[rumbling]

What better way to get the whole g*ng in

than with a drone.

But what science will
this snapshot demonstrate?

[glass shatters]

[electricity crackling]

[glass shatters]

Did you guess the science this flying
photo op is about to show us?

Say cheese.

[woman] Ah!

[Dallas] Yes, it's trajectory
estimation.

The drone operator here
is watching the drone

but estimating the trajectory of an
object coming straight at you is tricky

because you only have its
relative increase in size for reference.

[camera shutter clicks]

Oh-oh, that's a keeper.

[glass shatters]

[electricity crackling]

[glass shatters]

Have you ever wondered
what a power line looks like

when it's a bit cross?

Well, wonder no more.

Because that tree has just made
the mistake of tangling with one.

And now...

[men, off-screen] The tree is on fire!

[Dallas] Yes, it is.

But whilst they look enchanting...

don't hang about too long...

[loud expl*si*n]

...because they also do that.

With up to around 6,000 times thevoltage
of your average household appliance,

when a power line goes wrong,
you're gonna know about it.

And now, you're gonna understand why.

If an object bridges power lines,

it offers a shortcut

allowing a large amount
of current to flow through

and short circuit the line.

But there doesn't even need
to be contact to cause a problem.

Normally, electricity remains
safely within lines

because air is a good insulator
and won't conduct it away.

But if lines get too close to each
other,

the air between can become ionized

making a conductive plasma

and causing arcs that can erupt
in an expl*sive blast.

Yep, that all sounds pretty terrifying,

and did you know
that electrical signals can travel

through these lines
at two-thirds the speed of light?

So, one moment you have
a delightful drone.

And the next...

[electricity crackles, distant
expl*si*n]

...you have a bridge.

As soon as the drone connected the
lines,

current took the shortcut...

[electricity crackles, distant
expl*si*n]

...and its little


[men, off-screen] Wow!

[Dallas] I know,
either a power line is arcing

or the cub scout troop
has left a mess again.

[man 1, off-screen] Look at it arcing
between the two trees right there.

[man 2, off-screen] Oh God!

[Dallas] Yep, because the tree is
offering

the current a shortcut to the ground,

so the current flows through it
causing arcing in the ionized air

and a campfire you wouldn't want
to toast your marshmallows on.

But when that tree burns through...

the circuit breaks.

[men, off-screen] That was crazy.

[Dallas] No, it was simply
logical science, my friend.

Over in the suburbs,

a man is entranced
by the spectacular light show

at the back of his garden.

[loud explosions]

It's at this point he's now wondering
if he has a clean pair of underpants.

The arcing power line behind that bush
erupted in a stunning arc blast...

[loud explosions]

...with temperatures reaching
thousands of degrees.

So it may be safer
to stick to watching telly.

[bell rings]

[hissing, bubbling]

[shushing]

Settle down, I can wait all day.

It's time for your science lesson

where we focus
on one particular scientific principle.

Can you guess what it is
from the following clues?

Unhygienic parenting shortcuts...

[announcement in foreign language
on PA system]

...this savvy traveler...

...and a rude awakening.

Please don't try this yourself.

Yes, we're talking about partial
vacuums.

A perfect vacuum is a space
in which there is

absolutely no matter whatsoever.

That is pretty much impossible to
achieve,

unlike a partial vacuum

which a space in which
the average pressure of a gas

is lower than the surrounding pressure.

The science of which
can be ably demonstrated

with one of these.

As a vacuum cleaner's fan
forces air out from a chamber,

the pressure inside becomes lower
than the pressure outside,

creating a partial vacuum.

Air from the outside rushes in
to balance this out

bringing other matter with it.

The faster the fan,
the lower the pressure inside

and the more powerful the suction.

If the rush of air is sealed off,
adhesion can be created

as the higher pressure air
pushes on the obstruction.

Right, straight into the quiz.

Question one, how is
a partial vacuum created?

The clue is that glove.

As it expands and... explodes.

Oh, how disappointing.

[glass shatters]

That's better.

As air is sucked out of the chamber,

the pressure inside becomes lower
than the pressure outside,

resulting in a partial vacuum.

More pressure inside the glove
makes it expand.

More pressure outside the glass...

[glass shatters]

...makes it implode.

Lovely hat.

Question two, what happens
when you seal a partial vacuum

against another surface?

This science-loving cephalopod
is going to demonstrate

with his assistant
and close friend, Nikolaus.

The professor's suckers make
a strong seal on Nikolaus' mask

before expanding their volume
to create the pressure difference

resulting in adhesion.

Well done, Professor. You can let go
now.

I said you can let go.

Aww, they really are close friends.

Final question, number three,

what happens when you suddenly introduce
a pressure difference?

The trip of a lifetime.

Hmm, I wonder what that tiny window's
for.

Oh, it's for getting
your camera sucked out of.

The air pressure outside the window
is lower than the air pressure inside

and the higher
the velocity of the aircraft,

the greater that pressure difference

and therefore the more it sucks.

And that, my friends, is your lesson
on partial vacuums.

I hope you were paying attention.

Oh, for goodness sake.

[laughter]

[electricity crackling]

[creaking, clanging]

[Dallas] As you probably expect,

I've finally nailed the reverse
crossover,

the matrix, and the air jester,

and now I'm ready to learn
my next football freestyling trick.

No, too complicated.

A little silly.

Oh, that's it, the around the world.

Tap the ball, fling your foot
around it, and catch it.

High heels are optional.

As are friends.

[laughter]

[Dallas] Skill on the other hand...

-[boy] Ah.
-[Dallas] ...is essential.

And that comes with
understanding the science.

The big players here being elasticity

and unstable equilibrium.

A football's elasticity means
it conserves a lot

of the kinetic energy transferred to it.

So here, only a little force
is required to elevate the ball

to just below the waist.

This allows his foot to complete
a wild elliptical path

right around the ball...

and catch it.

Trickier still, on just one leg,

it would take only a small force
to unbalance him.

Simply standing up, you're already

in what physicists would call
"unstable equilibrium."

Standing on one leg even more so.

But let's start with elasticity

and remember, a football conserves
so much energy

you only need to kick it
with a little force.

That was a lot of force
and in the wrong direction.

Try a little more vertical.

Okay, good, but I meant the ball.

Oh, and another thing,
that is not an elliptical path.

Right then, on to equilibrium.

Nice.

[man] Oh.

[Dallas] Oh, never mind.

Still, you did take us
to unstable equilibrium page two.

On one leg, you're in
highly unstable equilibrium,

we know that.

But then landing on one leg
on top of an elastic sphere,

well, that's extreme unstable
equilibrium.

[man] Oh.

[Dallas] You might have
a sore behind, my friend,

but you have a bright future.

[electricity crackling]

[creaking]

In 19th Century Finland, so legend has
it,

bands of thieves raided villages

throwing the women over their backs
and then disappearing into the woods.

Now, you might consider kidnapping
a little bit too bleak

to base a family friendly
sporting event on.

But they don't.

This is a wife-carrying championship.

Originating in Finland
but now popping up all over the world.

[man] Oh!

[Dallas] Thankfully these days,
it's no longer just men hoisting women.

Anyone can lift anyone
and all techniques are welcome,

from the classic shoulder carry
to the piggyback.

But according to science,
your best bet might be

a peculiar inverted method
called the Estonian lift.

When carrying someone,
the combined center of mass is raised,

meaning even a small lean...

could move it outside
the base of support of the feet.

With a piggyback, he must lean forwards

to keep the combined center of mass
over the base and remain stable.

But the Estonian lift naturally keeps
the combined center of mass

more in line with the base...

for a more balanced running gait.

When training for the big race,

it's good to test your technique
at smaller local events.

Like this one,
but contrary to the science,

they're going with the piggyback method.

Will it work?

[men, off-screen] Ready? Set? Go!

[laughter]

Good race! Good race!

[Dallas] Not that good.

[man] Hey, we won!

We won!

[Dallas] Really? Let's see.

To compensate for the combined center
of mass moving backwards,

the carrier leaned further forwards
but actually overcompensated.

[man grunts]

[Dallas] Although, yeah,
they did win but at what cost?

Right, on to the main event.

[men, off-screen] Go!

Hey!

[Dallas] Good combined center
of masses, people,

but here comes the real test...

the muddy puddle.

[woman coughs]

[Dallas] With that high
combined center of mass,

it only takes a little stumble

for it to fall outside the base,

resulting in a refreshing soily drink.

That's not chocolate, my friend.

Now this chap wouldn't dream
of dunking his partner.

He'd rather slam her face
into solid earth.

A lack of friction underfoot
meant he leant too far back...

easily pushing the combined center of
mass

outside his base.

But, look, technique isn't everything.

[crowd, cheering]

[Dallas] You do also have to run.

[man panting]

[glass shatters]

[energy crackling]

[glass shatters]

[Dallas] And that's your lot,
now please do not attempt

any of the dangerous stunts
you have just seen.

Revered naturalist
Charles Darwin once said,

"I love fool's experiments,
I'm always making them."

But I doubt he ever did any of this.

[laughter]

[crowd] Oh!

[laughter]

[woman] Ah!

[loud explosions]

[horn honking, tires squealing]