03x12 - Bikes, Fishing and Slalom

[bunniefuu]

[Richard]
This is the Science of Stupid.

[electricity crackling]

Yes, this is the show that blends science
with stupidity.

-Watch as wannabe stuntmen and
women... -[screams]

...risk all
in the pursuit of cheap thrills,

with predictable
and not-so-predicable results.

We reveal what went wrong and why,

with the help of scientific principles

like compression,
Bernoulli's principle of lift,

and that little terror, gravity.

So heed the warnings,
listen to the science.

Please, do not try any of this at home.

Watch out...

It's the Science of Stupid.

[electricity crackling]

[lively music]

In this show, we'll see...

how to control your moment of inertia
and how not to.

How a loss of traction can aid turning

and crashing.

Plus, what happens when you combine
mass with velocity.

[screaming]

It's not pretty.

[roller skater] Argh!

[Richard] But first... this.

[glass shatters]

[electricity crackling]

It's estimated that rock climbing
is enjoyed by around 9 million people

each year in the US alone.

A select few of that number
love it so much

that they feel compelled to do it
no matter where they are,

with or without ropes, or rocks.

Here's one of those people,

French Spider-Man Alain Robert,

climbing the 689-foot
Tour Montparnasse in Paris.

I've no idea why.

And here's a random bloke
scaling a block of flats

somewhere in Russia.

[man] Ah!

[Richard] He's not as good as Alain.

The urban climber, a person determined

to scale any object or structure
in their path,

is a bit like Spider-Man,
except without any of his special powers,

so you can see
why this is an extremely dangerous

and rather ill-advised activity.

But for the sake of scientific
knowledge alone,

here's how it works.

[electronic music]

To be climbable, a structure must be able
to support the force of his weight,

and provide a sufficient
coefficient of friction for good grip.

To climb, he uses enough points of contact
to spread the force of his weight.

He grips hard, because
the force of his grip

times the coefficient of friction
equals frictional force,

and keeps flat against the structure

to reduce the chance of a turning effect
ruining his day.

Now, that science in mind,
the first thing any urban climber will do

is carefully select
the structure he's about to climb

by asking himself two key questions.

Does the climbing surface offer
a high coefficient of friction?

[lively music]

-[man] Ah!
-[man laughing]

[Richard] If it's a glass windscreen,
the answer is no.

Second question: Will it support the force
of my weight?

[man, off-screen] Go!

[bleep]

[Richard] No. No, it won't.

[man] That came from up there.

[Richard] Yeah, I know that,
but where did he go?

[man, off-screen] Go.

[Richard] That went badly. Onto technique.

And remember those three key points:

Maximizing friction, keeping nice and flat
against the climbing surface,

and having plenty of points of contact.

[electronic music]

Just two points of contact here.
Is that enough?

[man] Ow!

[Richard] Not really, no.

[rock music]

Remember, more grip force
equals more friction.

So by gripping hard
with both hands and both feet,

he can maximize frictional force.

Hang on, what's he doing now?

[man] Ah!

[Richard] I wouldn't swim in there
if I were you.

It's Super Bowl, and for some reason,

this chap is hoping he can get in
through that window.

[crowd] Let him in! Let him in!

[Richard] So is everyone else.

Oh, looks like he's in luck.

[crowd] Yeah!

Oh!

[Richard] No, he's not.

He kept flat against the wall
to avoid a turning effect,

but his foot slipped,
which led to a falling effect.

[electricity crackling]

Back in the '30s, George Nissen
developed the modern trampoline,

making acrobatic feats like flips
a possibility for almost anyone.

I've no idea if George
included safety instructions,

but here are the basics.

First, always check for signs of distress.

[man, off-screen] Oh! Oh, [bleep]!
Oh, [bleep]!

[Richard] There's a little tear there.

Ensure the trampoline
is appropriate for your size...

[lively music]

...and age.

And if you do nail your flip
on the head...

[man] Ow!

[Richard]
...don't try to multi-task.

Clearly, attempting a trampoline flip
without training

can result in a lot of pain.

So maybe George should have
kept his invention to himself.

But since he didn't, here's the science
behind the perfect trampoline flip.

As a trampoline deforms,
it stores elastic potential energy.

[electronic music]

The further he falls,
the more kinetic energy he has,

and the more
air time he'll have for the flip.

To help his rotation, he tucks in tighter,
increasing angular velocity

so he can spin up to three times faster.

The record for consecutive
trampoline somersaults is 3,333 flips,

but even for one,
you're after a nice, big bounce.

This doesn't bode well.

[man] Ah! Ow!

[Richard] You want more kinetic energy?

Gonna need a bigger trampoline.

Okay, better,
but remember, the less...

-[man, off-screen] Oh, h*-h*!
-[Richard] ...you tuck in,

the slower your rotation.

He just about got away with that.

[man, off-screen] One more.

Three's a charm.

[Richard] No, I think two was the charm.

Three was something else.

-He's got it.
-[man] Arh!

-[man 2, off-screen] Ow!
-[Richard] He had it.

I don't know, but I'd say this
isn't particularly tucked in.

[man 2, off-screen] Ow!

[Richard] Resulting in
insufficient rotation,

with a lot of forward momentum...

-[man 2, off-screen] Ow!
-[Richard] And, uh, yeah. That.

A vertical landing can also help,

because if you impact
a trampoline at an extreme angle,

all that stored elastic energy

will bounce you off
at an extreme angle too.

For example...

Zero degrees, zero degrees,
zero degrees...

[spectators, off screen]] Ah!

[Richard] Forty-five.

[woman, off-screen] You idiot.

[Richard] Well, she does have a point.

[spectators laughing]

Nice!
But where's your trampoline?

Ah, there we go.

Great vertical bounce, excellent tuck.

You, sir, get an A-star for science.

-[man laughing]
-Okay. I'm taking the star back.

[man laughing]

[electricity crackling]

She's about
to prom-propose to him,

but can you guess the science
we're going to see?

[glass shatters]

[electricity crackling]

So, did you work out what science

this unexpected prom-proposal
is about to demonstrate?

-[woman laughing]
-[man] Ow!

[Richard] Surprise! It's impact force.

By jumping on him, she conserved momentum,
transferring some to him.

But landing body part by body part...

can reduce the average force
of the impact, a little.

Will he say yes?
I'd have to think it over.

[man groans]

[electricity crackling]

You know that feeling?

You're halfway to work,

you think you might have left the gas on.

Always best to double back and check
just to be safe.

[upbeat music]

Uh, I don't think your house
is down that way.

Want more velocity
and more risk in your U-turns?

Well, there's a technique
that'll do just that.

And it's this.

The textbook handbrake turn.

And this...

the comic handbrake turn.

Pulling off a handbrake turn
relies on precise control of traction.

It is highly dangerous, so to demonstrate
the science behind it,

here's a professional precision driver.

[dramatic music]

First, he builds momentum
and turns sharply,

before applying the handbrake
to lock up the back wheels.

The car's momentum causes the back wheels
to lose traction,

and they slide out due to inertia.

As he loses momentum,
traction is regained.

He releases the handbrake and he's away.

Needless to say, this kind of U-turn

should only be attempted by experienced
stunt drivers, and never on the road.

[tires squealing]

[man 1, off-screen] Whoo!

[man 2, off-screen] ****** hell!
That were well good!

[Richard] Safe to say these people
are not experienced stunt drivers.

Still, he managed enough momentum
to overcome traction on the back tires,

just not enough for a U-turn.

Which is just as well,
since he was inches from disaster.

[man 1] Very well close near miss.
I bet that's an inch!

[Richard] All right, an inch.

[engine roaring]

It's night, and the famed
Cincinnati Drift King is in town,

demonstrating
perfect loss of traction on every turn.

Except that one.

[man, off-screen] There is no way that
he just did that.

[Richard] No, he did. Look.

Lose traction on the back wheels,
and you get a tight turn.

Lose it on the front wheels, and...

[man, off-screen] No. No, no, no, no, no,
no, no, no, no, no, no, no, no, no.

[upbeat music]

[Richard] On a wet, slippery surface,
losing traction is a doddle.

But controlling your turn is a fiddle.

The tires' coefficient of friction
in the wet

is roughly half of that in the dry,

and holding your arm out of the window
doesn't help either.

Best to keep it on the steering wheel.

Needless to say, don't try this yourself.

[bell rings]

And now, it's time for
today's science lesson,

the part of the show where we pop
a particular scientific principle

under the microscope.

Today's theme involves some
really shocking science.

Here's a clue.

[man] When I say, just turn the key
and the engine should start.

-But don't do it before!
-[boy] All right.

[passenger, off screen] Go!

[man] Ah!

[man] No! not before!

[Richard] Yes, today's lesson is on
electrical currents.

Suffice to say you should never
mess around with electricity.

It is extremely dangerous and can cause
serious harm, and here's how.

Electric currents flow from
high to low voltage

through conductors, like metals,
but not insulators, like rubber.

The human body is around 70% water
with salts in it,

making it a fairly good conductor.

Voltage is the force behind the flow.

Current is the flow rate itself,
and it's the current that does the damage.

I hope you were paying close attention,
because it's time for a test.

Question one: Can you name any conductive
and non-conductive materials?

I'll start you off.

[lively music]

A wooden broom handle is not conductive.

-[electricity zapping]
-[girl] Ai!

[Richard] But a metal one is.

[man 1, off-screen] We got an electric
fly swatter set up over the toilet.

[Richard] Now, why would you do that?

[man 1, off-screen] We got our main man
here that's about to pee on it.

[Richard] Of course.

Now, pure water is not conductive,
but what about urine?

-[electricity zapping]
-[man 2] Ah!

[Richard] Well, what did you expect?

It's the salts in urine
that make it so conductive.

[man 2] Ah!

[Richard] I'd cut down on your salt, mate.

Second question: Is the human body
a good conductor or a poor conductor?

Let's see if these guys have the answer.

[man 1] Oi Josh, now you come in!

[Richard] They're inexplicably
clinging to an electric fence.

[man 2] Go!

[Richard] They seem fine...

-[electricity zapping]
-[all screaming]

Until Josh came along.

Insulated platforms stop the electricity
flowing through them,

until their uninsulated friend
joined the party

and completed the circuit to the ground.

-[electricity zapping]
-[all screaming]

They won't be inviting
Josh again.

[boy] Ah!

[Richard] Electric fences
carry up to 10,000 volts,

and can cause acute discomfort
to a large horse,

so please, do not touch.

But question three: Is it voltage
or current that causes you pain?

[Kevin] My name is Kevin and today
I'm going to Tase myself...

...just so you guys know
it's a real Taser.

[Richard] Don't worry, Kev,
I'm quite happy to take your word for it.

[screams]

A 50,000 volt Taser
only delivers around 0.0021 amps,

a small current, but enough to
really hurt a grown man...

[screams]

...and Kevin.

[groaning]

And so ends our lesson
on electrical currents.

-A lesson some people...
-[man] Ah!

[Richard] ...will never learn.

[man] You got me again!

[Richard] Are you surprised?

[woman, off-screen] He's stressing.

[Richard] Maybe just shocked.

[woman, off-screen] How are you?

-[man] Not before!
-[boy] OK.

[glass shatters]

[electricity cracking]

[Richard] Can there be a more relaxing way
to spend an afternoon

than kayaking down a river?

[rock music]

[kayaker] Ah! Uh!

Uh!

[Richard] Yes. Yes, there can.

In fact, a mouthful of river water
is the least of your worries.

There's also sinking,
dropping over waterfalls,

and being dashed against rocks.

Avoiding all of that depends largely
on balance and buoyancy.

Kayaks have a narrow hull,

reducing hydrodynamic drag going forwards,

but giving them poor
side-to-side stability,

especially in turbulent water.

By displacing water, a kayak generates

a buoyant force that balances
the force of its weight.

But leaning the center of mass sideways
can disrupt the balance of these forces,

causing a capsize.

Balancing over that narrow hull is tricky,

but it's a whole lot simpler if you stick
to a nice, calm body of water.

Not particularly calm,
but let's see how we go.

Not well.

That turbulent water pushed him
perpendicular to the flow,

increasing drag, so his center of mass
lent a little too far and over he went.

And back up again.

No, sorry. Back down.

There he goes.

If you do tip, pushing the paddle down
on the water can help.

-It's called a brace.
-[kayaker 2] Ah!

[Richard] Okay, brace.

Hey, nicely done.

-Okay, brace.
-[kayaker 2] Ow!

[Richard] Oh, dear.

That's going to be a problem.

[kayaker 2] Ah!

[Richard] But there is a place where
the water can be even more energetic.

It's called the sea.

[rock music]

Where's he gone?

Ah, there he is.

Safe and sound.

I wouldn't sit there.

Okay, remember,
the calmer the water, the easier it is.

[kayaker 3] Ah! Uh!

[Richard] Except, perhaps, for him.

[kayaker 3] Sarah, this has never
happened and if I move it sinks lower.

[Richard] Yep, that's because
your kayak is filled with water,

reducing its buoyancy.

[kayaker 3] Sarah, I don't know what to
do.

-[Sarah, off screen] I can't help you.
-[Richard] Well, how about moving

your center of mass
to the middle of your kayak?

[Sarah, off screen] Yeah, that's it. See?

-[Richard] Okay, that didn't work.
- [Sarah, off screen] Oh my God!

[kayaker 3] Oh my God, I don't know
what to do.

[Richard] Neither do I.

-[kayaker 3] Oh, no! Oh.
-[Sarah laughing]

[electricity crackling]

[Richard] To any Neanderthals out there
who still regard

the female of the species as fragile,
helpless creatures, a word of warning,

they're not, really not.

Especially when it comes to roller derby,

a sport where two teams of roller-skaters
attempt to overtake each other

with some gentle persuasion.

Lots of gentle persuasion.

If you still fancy a go at roller derby,
and you don't want your competition

to get the better of you,
you need to master the block.

[upbeat music]

Skaters lean in a turn
to counter centrifugal force

wanting to throw them outwards.

To block, her opponent in red
uses her momentum to apply force

above the center of mass,
creating a turning effect,

or moment, which knocks her off balance.

First off, momentum.

The key equation being that momentum
equals mass times velocity.

But what does that mean in practice?

[roller-skater 1] Get out of my way!

[roller-skater 2] Argh! Ow!

[Richard] Yeah, I think she just
won that one.

[roller-skater 1] Yeah, we'll see.

[Richard] No, you definitely won.

[roller-skater 2] Uh!

[Richard] Combining mass with velocity
gave her momentum

equivalent to a 14-pound bowling ball
traveling at about 100 miles an hour,

which she then shared with him.

[roller-skater 2] Argh! Ow!

[Richard] Cheer up, fellow.
There's always golf.

[roller-skater 2] Uh!

[Richard] To get that perfect
turning effect, or moment,

you need to aim your momentum
at the right place.

Remember, a good shove above or below
the center of mass,

and your opponent is going down.

Or you are, if you completely miss.

Okay, let's try a block on someone else.

Right, kind of worked,
but that's more of a cuddle.

Everyone loves a cuddle.

Right, so momentum and turning effect.
Have you got that?

[woman screaming]

I'd say that's a yes.

[glass shatters]

[electricity crackling]

And that's all your science and stupidity
for now.

Please do not attempt to copy
any of the stunts you've just seen.

Mishandling the laws of science
can only lead to regret.

If you need further proof, watch this.

[lively fiddle music]

[man screams]

[man] Ow!

[girl] Ai!

[all screaming]

[woman laughing]

[Kevin screaming]

[kayaker] No!