01x05 - Airbags vs Airheads

[bunniefuu]

RICHARD: Stand by
for the Science of Stupid.

- [electricity crackling]
- [glass shatters]

[alarm blares]

[reading]

Separating science stupid...

from science fact.

We'll meet the people
who fell out of the clever tree,

and give you the scientific detail

of exactly where they went so wrong.

Yes, this is the show that tells you
everything you need to know

about friction coefficients.

Expanding gases.

And, of course, levers.

Mess with science...

and it'll mess you up.

MAN: [bleep]

RICHARD: So watch and enjoy,
as the world's sultans of suffering

discover center of gravity.

- The expl*sive potential of gunpowder.
- MAN: [bleep].

RICHARD: And suffer the consequences.

MAN: Ah. Ah.

RICHARD: Science can swing you
on the pendulum of pain.

[screams]

Hold on tight.

This is the Science of Stupid.

- [electricity crackles]
- [glass shatters]

On this show, we'll see what happens
when there's not enough friction.

Give a practical demo
of hydrodynamic drag.

And show you why you should
never play with your ba*ls.

But first, this.

- [glass shatters]
- [electricity crackling]

Sliding down a slippery slope

can be poetry in motion.

Don't believe me? Check this out.

[man laughing]

MAN: Yeah, boy!

Congratulations all round,

but sadly slipping and sliding
doesn't always go to plan.

It sometimes goes to pain.

That might look like jolly japes
on a sunny afternoon,

but it shows a fundamental lack
of specialist scientific knowledge.

The science of friction control.

Here's why slip and slide
can easily become smash and smack.

Water can reduce the coefficient
of friction by two thirds.

It's called hydrodynamic lubrication.

That's slipperiness to you and me.

Add soap to the water
and it makes the water

up to three times more slippery.

Soap forms tiny spheres
that float in the water

and act like mini ball bearings.

But regardless of friction coefficients,

the slider needs to get moving
in the first place.

A run up or a slope will do the job.

A lovely summer's day
is the perfect opportunity

to investigate friction coefficients,

but take care.

Let's look at the results
of some recent experiments.

Watch out, move! Move!

MOM: I don't think it's slippery yet.

[mom laughing]

RICHARD: Your mum's right,
too much friction.

[laughing continues]

These ladies have got
their friction just right.

Ah. Whilst this jolly prankster
gets a lesson in impact.

What happens when you add soap?

That's slippery.

MAN: Oh!

RICHARD: Too slippery, in fact,
three times less friction than water.

Once you think you've cracked
your friction coefficients,

you can start thinking about your landing.

Absorbing the impact of your landing
is a very good idea,

as hitting the ground head first
carries a real risk of permanent injury.

- [man laughing]
- MAN 1: [bleep]

MAN 2: Definitely need
to pull that pool over!

RICHARD: Definitely.

Here's an ambitious slip and slide
as*ault course.

A slippery surface
covered with water and soap.

Remember, soap can further reduce friction
by up to three times.

For momentum, a powerful 4x4

that can tow a 3,300 pound trailer.

Has he correctly calculated
his friction coefficient?

MAN: Stop!

[bleep]

RICHARD: Well, yeah, I suppose he has

but he forgot to mention
stopping to the driver.

That low coefficient of friction
combined with too much speed

from the 4x4 means...

[man groans]

MAN: I completely missed the pool.

RICHARD [laughs]: Yeah. I couldn't
have put it better myself, 'cause you did.

There, look.

- [electricity crackles]
- [creaks]

Roundabouts.

A lovely way for children to have fun.

Wrong!

It's the perfect apparatus
to study the relationship

between circular motion,
momentum and human strength

with some bumps and bruises along the way.

There isn't a scientific law that says

if you smack him on the head
he'll go faster.

MAN: Holy...

RICHARD: But there is a scientific force
that you need to understand and apply

if you want to stay on a roundabout
spinning at speed.

[man laughs]

Centripetal force is the force
you must apply to stay on.

It's as simple as holding on,

well, it is holding on,

but holding onto a roundabout
isn't always simple.

The closer you are
to the center of the roundabout,

the less centripetal force
is needed to cling on.

The further you go from the center,
the harder it is to hold on

because the roundabout
spins faster on the outside.

To make matters worse,
if you double the spin speed,

you need four times
the strength to cling on.

Remember, if you're hanging
onto a roundabout at the edge,

it doesn't take much of a spin speed

to produce the same G-force
you'd experience hanging from the ceiling.

Even at just 1-G, muscular fatigue means

it's just a matter of time
until you fall off.

But is anyone listening?

Two mistakes here.

This chap's forgotten that the roundabout
spins fastest on the outside.

He's also in a dustbin.

Ah, he's got it now, a central position.

Easier to hold on.

[bleep]

But the-the dustbin thing,
is still an issue.

You can turn a roundabout
upside down and make it higher.

[laughter]

But you will still need
centripetal force to hold on.

[laughter]

What was it we said about
doubling spin speed?

Oh, yeah, it quadruples centripetal force
needed to hold on.

That's about 3-G,

in other words you have to hold against
three times your own body weight.

Or not.

The boy in green knows he's the heaviest,

and will need the most centripetal force
to hold on.

But position on the roundabout
is everything.

His small friend at the center
can hold on.

At its rim, this roundabout
spins at about 2-G,

meaning most people can't hold on.

As he's just found out.

- [electricity crackles]
- [metallic thud]

[clatters]

Can you guess which scientific principles
are about to collide

with catastrophic results here?

- [glass shatters]
- [electricity crackling]

So what's going to happen
to these sand-loving off-roaders?

A steep hill covered in sand
offers very little traction.

Then the overworked engine catches fire.

Smothering those flames
deprives them of oxygen,

but the petrol fumes
are building up underneath,

and with a red hot engine...

[expl*si*n]

...at least there's someone in the car
with their foot on the brake.

Oh, no, no, there's not.

And that's good old gravity
taking the car at great speed

towards the spectators

who probably wish they'd gone
to the football instead.

I thought the most vital component

of roller blades was the wheels.

But some imprudent bladders
are sliding down rails

without using the wheels at all.

It's called grinding
and it can go horribly, horribly wrong.

MAN: Oh!

RICHARD: Okay, that could
have been construed

as someone just falling off a slide.

So here's some real grinding.

Oh, come on, this is going on now,

it's like one of those books
that's just too long.

Finish.

Yeah, all right, very cool.

So what separates grinding success

from grinding embarrassment?

It's science, of course.

To successfully start the grind,

skaters jump onto the rail with bent knees

that act like shock absorbers
and stop them falling straight off.

Grinding uses the frame
between the roller blade wheels,

not the wheels themselves,

to minimize friction
and maintain descent speed.

The key to a successful grind

is the skater keeping
his center of gravity low,

and directly above the rail,

as this gives him the best chance
of keeping his balance.

The grind is exited smoothly
by jumping off,

keeping the wheels in line
with the direction of travel.

I put a lot of trust in statistics,

and the fact that 34%
of all skating injuries

are a direct result of jumping or grinding

has persuaded me to give it a miss.

Of course, not everyone lives by numbers.

Yeah, it's-- it's a good start.

Weight above the rail.

But then it's weight off the rail,
weight on the concrete.

Remember what I said
about low center of gravity?

That's high.

So keeping his balance
for the turn is much harder,

but not as hard as the ground.

Center of gravity high,

nowhere near being
above the dumpster edge,

and a reminder of why protective clothing
is strongly advised.

[groans]

- [electricity crackling]
- [creaks]

The exercise ball.

Standard gym equipment
but also the perfect apparatus

to discover the springy properties
of elastic polymers,

and take a massive tumble.

[man laughs]

So what's the science
that makes exercise ba*ls bounce?

The molecules in the skin
of a PVC exercise ball

are shaped a bit like springs,
and act like them too.

The energy of the impact is stored

as the skin squeezes
against the ball's pressurized air.

The springy molecules
then release the energy

as it bounces back into shape.

If you smash into an exercise ball,

it can smash you back
with almost the same force.

Not convinced?
Here's some practical demos.

[yells]

Plenty of momentum,
and all that energy straight back at her.

Textbook!

Now he's considerably heavier than her,

and the energy of that impact
has to go somewhere.

Who said the age of chivalry was dead?

[woman screams]

WOMAN: Oh, my tooth came out,
my tooth came out!

RICHARD: Of course,
gender has nothing to do

with the outcome
of exercise ball collisions,

it is just a matter of weight.

The science is the same
for multi ball collisions,

but the results can be more spectacular.

Three guys stand their ground on impact

creating a counter force
with their bodies.

This guy doesn't.

And he gets ejected with the combined
momentum of all four of them.

That's what we like about science,

you can bounce ideas off people.

- [glass shatters]
- [electricity crackling]

Skilled divers are able to perform
gravity-defying aerial acrobatics

before entering the water
with barely a splash.

But combine blind enthusiasm
with limited skill,

and it's a very different story.

[indistinct chatter]

[man yells]

MAN: Oh, crikey!

They say
that hitting water at speed

is like hitting concrete.

[buzzer buzzes]

Well, not from
diving board heights, it's not.

Think about it.

You've gotta jump from 30 feet.

What would you rather land on,
water or concrete.

- [man yells]
- I rest my case.

That said, hitting water
at the wrong angle

can do some nasty damage
to soft tissue and skin.

To understand why,

you need to get your head
around hydrodynamic drag.

Hydrodynamic drag refers to the resistance

an object experiences
when it passes through water.

An object that has a small, sharp front
in contact with the water

has relatively low hydrodynamic drag

as it experiences little resistance.

An object that has a large
and blunt front in contact with the water

has more drag, and more resistance.

That's why divers are trained
to enter the water like this.

Near vertical with minimal surface area
hitting the water.

Think of an arrow shot into a river.

And why they're not trained
to enter the water like this.

Think of a grand piano...

falling into a canal.

In fact, belly flopping like this,
at 30 miles an hour,

can increase drag by up to
seven times compared to diving.

In practical terms, it stings a lot.

- [glass shatters]
- [electricity crackling]

Horse riding.

Ancient, noble, majestic even, I love it.

I could watch it all day,

but why anyone would actually
want to do it, I've no idea.

Is that because just
getting on can be dangerous?

[neighing]

Is it because in the US alone
around 100,000 people

are taken to hospital
with horse riding injuries each year?

No. The main reason I avoid riding horses

is because things like this can happen.

Well, that's just horse play.

No, that's, that's not.

Stop that.

I'm embarrassed.

That actually happened to me,

well, to the horse I was rid...

I don't wanna go back there.

Despite overwhelming evidence to suggest
getting on the back of an animal

that can weigh up to 1,000 pounds

and run at over 40 miles
an hour is a bad idea,

some people are still not convinced.

If that wasn't bad enough,

they're attempting jumps on horseback.

[bleep]

A partial success at best,

and a complete misunderstanding
of the science of parabolas.

A horse's jump involves three main phases.

The take-off,

suspension when the horse
and rider are in the air,

and landing.

These three phases combine
to make the jump parabolic.

That's basically its upward
and downward path.

For a perfect jump, the apex
or high point of the parabola

must be directly above
the fence or obstacle.

In a nutshell, the take-off
needs to be perfectly timed.

So shall we see some riders
and horses getting it just right?

Hang on, where's the fun in that?

Too early a take-off and there's no chance

of reaching the apex of the parabola
at the right point

and no chance of looking remotely cool.

And that's what happens
when there is no parabola at all.

Of course, it's not just early take-off

that results in incorrect parabolas.

MAN: Ooh. You all right?

RICHARD: Taking off too late
can result in an embarrassing failure

to clear even the tiniest of fences.

And we can't always blame the rider.

WOMAN: [gasps] Oh, [bleep]

RICHARD: This equine rebel
reckons he's got it licked,

but takes off far too late.

Clearly hasn't read his science books,

largely because horses
can't actually read.

WOMAN: [gasps] Oh, [bleep]

- [electricity crackling]
- [creaks]

Call me old-fashioned,

but I generally avoid
trying to drive up cliffs.

It turns out not everybody shares my fear
of vertical motoring.

Welcome to the world of rock bouncers.

Rock bouncers are basically
purpose built buggies

designed for tackling ultra-steep slopes.

Their main weapon is extreme power.

With engines that run on racing fuel,

they can generate up to
1,100 brake horsepower,

a seven seater family car
might have only 120.

Sadly, maximum power
doesn't mean maximum control.

A rock bouncer's long wheel base
makes it relatively stable

when it's facing up steep hills,

but its narrower axle width

makes it pretty unstable
when it veers sideways to the slope.

The problem is that rocky surfaces
are rarely smooth,

and a big bump can ensure
that the power from that massive engine

results in massive traction for the wheels
in contact with the ground,

flipping the vehicle.

So the mantra is fast and straight.

Easy to say...

but not so easy to remember it appears.

Ah, here we go.

Great power...

but-- but that's not straight.

In fact it is anything but straight.

And if you've got wheels in the air,

what will all that traction do?

That's right. It flips you.

Getting air on bumpy terrain
might be great for the crowd...

[crowd cheers]

...but not for stability.

Hence the roll cage.

And sadly, even with up to 1,100 BHP,

some gradients are just a step too far.

When the power runs out,
gravity takes over.

Yeah, can I suggest brakes?

Yeah, brakes, I said, like now!

Now! Bra...

Oh, okay, that'll do.

[screaming]

- [glass shatters]
- [electricity crackling]

[glass shatters]

Well, that's almost it for another
Science of Stupid.

There is just time for me to remind you

not to try and follow in the footsteps
of any of the brave

but misguided researchers
we've met in this show.

So if you are planning
to slide down a wet slope,

cling to the edge of a spinning roundabout

or just drive up a cliff,

do your equations and you'll soon realize

that it's safer to just go down the pub.

[yells]

- [cheering]
- [laughing]