03x07 - Drift Bikes, Beds and Catapults

[bunniefuu]

[Richard]
This is the Science of Stupid.

[electricity crackling]

Yes, this is the show where science
and stupidity collide.

As we look at the people
who put the dumb

in crash test dummies.

By analyzing their mistakes,

we'll explain the science
behind what went wrong and why.

[screams]

Exploring such principles
as velocity,

-angular momentum...
-[screams]

and even... troublesome, old gravity.

So be brave
and don't look away,

because this...
is The Science of Stupid.

[electricity crackling]

In this show,
we'll explore g-forces,

center of mass...

[man]
Oh, [bleep]!

[Richard]
The optimum trajectory...

and the not so optimum.

But first, this.

[glass shatters]

[electricity crackling]

Mention skiing,
and it gets me dreaming

about conquering those
vast, majestic mountains.

Gliding over glittering snow-covered
slopes beneath beautiful blue skies.

What I don't tend to think about
are concrete steps and metal handrails.

[screams]

But he does.

-And so does he.
-[screams]

[man, off-screen]
Yo, you good?

[Richard] No, I think
he's been better.

Surprisingly,
trying to ski on rails

or rail grinding,
to use the correct parlance,

has become a kind of
winter sports discipline

all of its own.

There's even a world record
for distance grinded

of 241 feet, 7 inches.

[screams]

That wasn't it.

But it did have
a nice ring to it.

[screams]

See?

But if you are determined
to throw caution to the wind

and give this a go,

then you need to
listen to this science.

[upbeat rock music]

To rail grind on skies,

he needs just enough velocity
to get onto the rail

and start sliding.

Low friction is crucial,

as too much will
stop him sliding.

For stability,
he keeps his skis

perpendicular to the rail

and his center of mass low,
over the base of his support.

The wider or flatter the rail,
the easier that is.

So it's about getting
the take off velocity spot-on,

center of mass
in the right place,

and hoping there's not
too much friction.

Okay, let's start by
getting that velocity right.

[country rock music]

Are you ready?

[man]
If I fall, you have to help me.

[Richard]
That doesn't sound very ready.

-[man] Oh!
-[man 2, off-screen] You good?

[Richard]
And that's because he wasn't.

Too much velocity
caused and overshoot.

[woman]
Do you guys do this a lot?

[Richard] I hope not.

Good velocity here.

[man, off-screen] Oh!
You good?

[Richard]
But in the wrong direction.

Hitting the flat section

caused his momentum
to be redirected...

[slow-motion wail]

To the bottom of the steps.

Yeah, it hurts.

[playful music]

[grunts]

Nearly.

But the change of direction
shifted his center of mass,

which shifted him.

Another go?

Even worse.
Who parked there?

For better control
of velocity and stability,

a horizontal bar might help.

[groans]

A vertical one will not.

Okay, maybe best
to avoid steps and handrails.

And walls.

Not to mention rivers.

[electricity crackling]

[clanking, rumbling]

Once something confined

to the realms of
a science fiction novel,

the drone,
or unmanned aerial vehicle,

is now something
that anyone can own.

[man, off-screen] Okay.

[whirring]

[upbeat music]

[Richard]
But not necessarily control.

[man, off-screen]
Oh, boy.

[whirring]

[laughs]

[child, off-screen]
It hurt me!

[man]
Oh, you're okay.

[Richard] Yeah, no thanks to you.

[lovely accordion music]

You can even
attach cameras to them,

allowing you
a whole new understanding

of the animal kingdom.

[grunts]

[whirring]

Not that you'll
always be welcome.

Or get your drone back.

[sniffing]

And drones now come
in all shapes and sizes.

[playful classical music]

Aw, that's pretty.

Is she a magical princess?

[heavy rock music]

Oh, no, Daddy's bought you
an evil fairy.

What a lucky little girl.

Yep, it seems that
quite a few of you

really haven't got to grips

with this whole
drone control thing.

So before you cause a major
air traffic control incident,

may I suggest
you take note of this science.

[rousing electronic music]

The rotors on a drone

deflect air downwards

and induce
higher air pressure below

and lower air pressure above.

This generates lift.

To change direction,

you speed up the rotors
on one side.

This increases
lift on that side,

tilting the drone
so that the lift force

has a horizontal component.

So controlling your drone

is largely down to
mastering that lift force.

Of course,
it's worth noting that

flying too close to surfaces,

like the ground,
walls, or ceiling,

can disrupt the airflow
into the rotors,

with potentially
expensive results.

But what are the chances
of that happening?

So you've just got
your new drone out of the box.

How exciting!

[man, off-screen] Okay,
everything says it's safe to fly.

[Richard] That's good.

[whirring]

-[man, off-screen] Whoa!
-[woman] Ah!

[Richard]
That wasn't quite so good.

[man, off-screen]
At least we got that on video.

[Richard] Yeah, you did.
Might want a bit more lift next time.

Let's have a look at someone

who's actually
got theirs flying.

Nice control,

carefully altering power
between those rotors.

Wha--hey!

[electrical pop]

Oh.

Might I suggest
a different flight plan?

Once you've got your lift
and momentum under control,

you can really start to see
why drones are so popular.

[smooth jazzy music]

[thud]

But possibly not with him.

[man]
****!

[Richard]
Definitely not with him.

Some people have taken
drone flying a stage further.

Part firework display,

part hunting trip.

I think you can safely say that

whoever's
controlling this drone

has got lift down to a T.

[dramatic music]

Although I would question
his sense of fair play.

[electricity crackling]

[metal creaking]

[crashing]

Can you guess what science

this spare wheel
is about to demonstrate?

[glass shatters]

[electricity crackling]

[crashing]

So have you guessed
the science we're about to see?

[man] Two, one!

[boom]

Where's the wheel? Where's the wheel?

[Richard] It's pressure.

-[man] Oh!
-[glass smashes]

[Richard] And gravity.

Rapidly building pressure
in the airbag

sends the wheel up,

and gravity sends it back down,

at 50 miles an hour.

[laughter]

Hilarious,

if it's not your car.

So don't try this yourself.

[electricity crackling]

[clanking, rumbling]

There are some things
in the world

which sand is very good for.

Beaches, camel riding,
the Sahara desert.

But there are some things
which sand isn't very good for.

Like riding a motorbike.

[yells]

[playful musical flourish]

Or, even worse...

[yells]

Attempting a jump on one.

Yes, whether it's
going for a jump

or simply riding
in a straight line,

motorbikes and sand
do not mix well.

But as always, science can help.

[engine revving]

Loose sand is granular,
with low sheer strength,

resulting in
an unstable surface.

[rock music]

When jumping,
the faster he leaves the ramp,

the less time gravity has
to rotate the nose downwards.

The closer the landing angle
is to 90 degrees,

the larger the impact force
on that unstable surface.

For jumping then, it's all about
getting up to speed.

Even when you're not jumping,

maintaining a reasonable speed

can help stop your bike

from sinking into
that dodgy surface.

Okay, got all that?

Then let's start with simply
driving in a straight line.

[rock music]

[bleep]

That didn't go too well.

Too little speed.

Over corrected steering.

[bleep]

Helmet full of sand.

Okay, bad start.

But let's try a little jump.

[man laughs]

[man, off-screen]
That was great!

[Richard] Mm, depends on
how you define "great."

Weight too far forwards,

resulting in a spectacular
forwards rotation.

[man, off-screen]
Do it again!

[Richard] Nah,
let's try a bigger dune.

Here's one!

Oh, dear.

Not enough velocity
and too much rotation.

Not nearly enough
sheer strength from the sand.

Proving that it's not just
good things that come in threes.

Is that one jump or two?

It's two.

He didn't get enough height
to clear that second peak,

and a little bump
caused an over-rotation.

So can you get too much height?

Yes, you can.

[lively music]

At over 30 miles an hour,

a not-so-ideal
landing angle

resulted in an unhelpful bounce.

I love sand between my toes,

but not in my teeth.

[bell rings]

[items clatter]

[bubbling]

Right, stop talking at the back,
looking out the window,

or fiddling with
your fluffy pencil case,

because it's time
for a science lesson.

And the subject of our lesson

connects all of
the following activities.

See if you can guess what it is.

[man, off-screen]
Go!

[Richard] A kid on a rubber band.

[playful lively music]

[man, off-screen]
Stop! Stop! Stop!

[Richard] A drift trike.

Which has just drifted
onto its side.

And finally,

a fairgrounds slingshot.

Hey, wake up.
It's the science lesson.

Well, if you hadn't
already figured out

what those three have in common,

it's that they've all
experienced g-forces.

Yes, you don't have to
be fired into orbit

for g-forces to have
a big effect on you.

So here are three facts
about g-forces

that might come in handy.

The first being
what they actually are.

G-force is a way of representing
the acceleration of an object

in terms of Earth's gravity.

One g is the acceleration
due to gravity

at the Earth's surface.

Force is equal to
mass times acceleration.

So the more g's you pull,
and the bigger the mass,

the greater the force you feel.

[electronic music]

In an average person,


in a head-to-toe direction

can force blood from the brain

and make you pass out.

So three very important things
to know about g-force.

And now a little test to see
who was really paying attention.

Question one:

what puts the "g" in "g-force"?

[playful music]

[wails]

Yes, it's gravity.

At rest, on the Earth's surface,

we're all at 1 g,

like him, relaxing on the beach.

[man, off-screen] Three, two, one.

[Richard] A concealed airbag
quickly increases that upwards.

[man, off-screen]
Are you okay?

[Richard]
Well, no, really not.

[man laughs]

Question two:

according to
Newton's second law,

what does force equal?

[playful horn music]

Yes, it's mass...

...times...

acceleration.

By some estimates,
a human cannonball

can accelerate so much

that they experience


Although sometimes
it might feel like more

on landing.

Finally, question three
of our science lesson:

g-forces can make you pass out.

But how many g's will it take?

["Hail to the Chief" playing]

In the 1950s,

Colonel John Stapp
of the US military

subjected himself
to forces of 46 g

in the name of science.

Which is more than enough
to make you faint,

or, in fact, almost die.

Around 60 years later,

these two on a slingshot
are about to experience

their g-forces
in the name of fun.

[screaming]

In fact, it only takes


to make your average person
pass out.

But since slingshots
rarely get up to 5 g,

he's probably just very scared.

[screaming]

I wonder what he's like
with spiders.

[playful music]

[screaming]

[laughing]

And here ends
our lesson on g-force.

[playful musical flourish]

[screams]

[glass smashes]

[electricity crackling]

[crashing]

For as long as
duct tape has existed,

people have used it in
all sorts of sticky situations.

Some people use it
to seal cracked pipes,

others to tape up cables,
and others still

to demonstrate their
unbelievable powers of escape.

[playful accordion music]

[man] So you put your hands
on top of your head like this...

and you go straight!

And you go straight down!

[Richard]
Yep. Unbelievable.

[man laughing]

It doesn't take a genius
to work out that

duct tape has
two fundamental properties.

It's very sticky,
and it's very strong.

And here's why.

[electronic music]

As duct tape's
adhesive molecules

spread over a surface,
it sticks.

Pressing increases
the surface area,

over which those molecules work,

sticking it harder.

By overlapping the tape,

it's possible to transfer
the load more effectively

for greater overall strength.

The cloth backing distributes
load between the threads,

making it stronger.

And if that force is
acting in line with the tape,

its tensile strength
is at its most effective.

So remember,
it's all about adhesion,

transferring that load

and making the best use
of the tape's tensile strength.

Not sure this is the best use.

[man, off-screen]
How do you feel right now, Dan?

[Dan]
I'm hanging in there.

[laughter]

[Richard] That tape
is firmly pressed down,

for more contact with the wall,

and so greater adhesive bond.

Same deal here.

Only that tape...

might need a bit more pressing.

[dainty music]

Oh, look,
a duct tape baby swing.

[man, off-screen]
I don't know how big babies are.

[Richard] A bit bigger than that.

[woman, off-screen] Is it working?

[groans]

[Richard] No, it's not.

Without enough tape
to distribute your load,

it wasn't strong enough.

But don't worry,

actual babies
are smaller than you.

[playful music]

They've made a door
out of their duct tape.

[woman 1] Ready?

[woman 2] She'll make it through!

[Richard] No, she won't.

[screams]

Because their door
is both sticky and strong,

thanks to good load distribution

and the tensile strength
of the tape.

[screams]

Maybe go under next time?

Now, bearing in mind
what we've learned,

what would be
the stupidest thing

you could make from duct tape?

I don't know,
maybe a bulletproof vest?

[soft dramatic music]

[man] I'm going to have it shot at me
without even testing it first.

[Richard] Why not, it's not like
anything could go wrong.

-[woman] One.
-[g*n fires]

[groans]

[Richard] Apart from that.

And that's because
the tape's tensile strength

can't stop it being pierced.

So the BB pellet
went straight through it,

and into, well, him.

[man] I might give up on this.
That doesn't feel good.

[Richard] Mm-hmm.
Doesn't look that good either.

But then, a second
belly button rarely does.

[electricity crackling]

[metal creaking]

[crashing]

Ask me what calisthenics is,

and I could tell you that
the dictionary defines it

as "the use of
gymnastic exercises

to achieve bodily fitness
and grace of movement."

Or I could simply say,

it's this.

Annoyingly fit people using

overdeveloped body strength
alone

to do useful stuff,
like this, for fun.

[rock music]

But in case you're blessed
with overconfidence,

and are thinking
"I can do that"...

[comic whistle]

Well, that's what he thought.

Now, call it a hunch,

but I am just
getting a slight sense that

maybe not everyone would be able

to master calisthenics
straightaway.

So let's concentrate
on the science

behind one key element:

the inverted push-up.

Here it is.

First, he needs
just enough momentum

to get him up into position

without over-rotating.

The more his legs are tucked in,

the smaller the turning effect
his muscles have to overcome.

[upbeat rock music]

And to maintain that position,

he needs his center of mass

to be above his base of support.

Shall we begin by
getting into the right position?

Now, when learning,
it's always best

to start in a safe environment.

[playful jazzy music]

Or a kitchen top.

Please yourself.

Come on, now.
A bit more momentum.

Maybe a bit more.

-[crashing]
-[cat shrieks]

Maybe a bit less

and not in the kitchen.

The living room.

[man] Yeah! Oh, ****!

[crashing]

[Richard] Possibly not.

[man] Was that the TV?

[Richard] Yeah, it was.

And thanks to
a wayward center of mass...

[man] Oh, [bleep]!

[Richard] It was also the clock.

Ah, a gym.

That's more like it.

[drumroll]

[groans]

Oh, that was less like it.

If your push-up
isn't particularly stable...

[groans]

At least do it
on something that is.

[upbeat music]

Now, this looks more promising.

Great upper body strength.

[wails]

Not such a great
awareness of center of mass.

But master momentum
and center of mass,

and calisthenics can be used
for practical purposes.

[playful whistling music]

Uh, like dodging the bus fare.

I think that's what he's doing.

All right, don't push it.

[glass smashes]

[electricity crackling]

[crashing]

Quite a lot
for us all to think about,

I'm sure you'll agree.

And provided
we just stick to thinking,

it'll be fine.

It's when you start the doing

that it can all
get a bit, well, stupid.

Good bye.

[lively fiddle music]

[engine revving]

[bleep]

[wails]

[engine revving]

[man laughs]

[woman]
Oh, my God!

[laughing]

[grunts]

[whirring]