01x10 - Bungee Cord Snaps

[bunniefuu]

RICHARD: Stand by.
It's the Science of Stupid.

- [electricity crackling]
- [glass shatters]

[alarm blares]

[reading]

Yes, this is the show
that beats the twin paths

- of science and stupidity.
- [screams in pain]

Over the next half hour,
we will see what happens

when those two paths collide.

We celebrate off piste investigations,

into inelastic collisions,
expanding gasses,

Newton's first law, and angular momentum.

Find out the hard way.

If you try to break
the laws of science...

WOMAN: Oh, my God!

RICHARD: ...They'll break you.

So, people, remember,

scientific ignorance can badly
affect your judgment.

[laughter]

And will not make you more popular.

Now, strap in for the Science of Stupid.

- [electricity crackles]
- [glass shatters]

On this show, we'll see what momentum
can do to your golf swing,

how Hooke's law can affect your face...

Ohh!

RICHARD: ...And what happens when
you forget about interlocking stability.

But first, this.

- [glass shatters]
- [electricity crackling]

Gymnastic bars.

Dangerous enough in the gym,

so why did they put them in public places
like parks or beaches?

It's great when there are
gym bars at the beach.

You can show off your six-pack

and make a big impression with the ladies.

Well, he certainly made
a big impression on the beach...

with his head.

They may be simply constructed,

but this kind of apparatus
are especially unforgiving

because they demand a high level
of commitment

and skill to master.

Success at gym bars relies on gymnasts

building up their momentum on the bar

and using it to spin themselves
through the air.

Let's look closer.

Two kinds of momentum are involved.

Angular momentum keeps you rotating.

Linear momentum determines
your speed and direction of travel

when you let go.

Going from totally vertical above the bar

to totally vertical below it,
the force you experience

is up to six times your body weight,

so you do need a strong grip.

Good rotation, plenty of angular momentum

and a strong, double-handed grip here.

He was OK until he tried a trick.

With only one hand on the bar,

his linear momentum sends him flying.

Come on, people.

Get a grip.

Didn't we just say
gymnasts experience forces

of up to six times their own body weight?

It's like being on a roller-coaster.

Scream if you want to go faster.

He forgot to scream.

Once you've mastered holding on,
you need to know when to let go.

In order to land the right way up,

you need to build up enough
angular momentum

before you release

and still have enough linear momentum

to move away from the bar,

which lets you land
elegantly on your feet.

Remember, it's all about timing.

So where did he go wrong?

He lets go too late,
so his linear momentum is too vertical,

meaning he's still too close to the bar.

Even with two eager helpers standing by...

his lack of angular momentum
makes him land on his head.

He's not gonna win any medals
with helpers like that.

This guy's good.

A pro gymnast can reach
about 40 revolutions per minute.

Impressive stuff.

- [crowd gasps]
- Oh.

He tucks in after he leaves the bar,
but opens out too early,

so instead of landing elegantly
on his feet,

he slammed down like a duck.

A dead duck.

- [electricity crackles]
- [creaks]

You can say one thing about stilt design.

It's come on in great strides.

Sorry, sorry.

We've come a long way from this.

Whatever it is.

Whether you use modern sprung stilts
or wooden sticks, it's all about balance.

When walking on stilts,

you must keep yourself from tipping

more than 15 degrees sideways.

You want to keep your center of mass
above your base of support

to stay upright as you move forward.

Stilt walking is hard enough as it is,

so there's really no need
to over-complicate it,

like these people.

He might need those crutches in a minute.

- MAN [screams]: [bleep]
- RICHARD: Yeah.

Walking backwards, he's put his bottom
outside his base of support.

[laughter]

And now it's on the ground.

MAN: You got it, man.

RICHARD: A skateboard isn't a solid base.

That's a case of a valuable lesson
learned the hard way.

On ice, there's less friction
to grip the floor.

[laughter]

You need solid ground
to keep your balance.

MAN: Oh, God!

If you're bored with two planks of wood
strapped to your legs,

you might want to try spring stilts.

None of that clumping around,
instead a graceful stride

with a spring in your step, literally.

Sprung stilts
efficiently store and release energy

to amplify your running speed.

Double the downward force

and you can double the compression
of the spring.

It's Hooke's law,

and the more elastic potential energy
that's in the spring,

the more kinetic energy is released
when the spring recoils.

Has he put enough energy
into his spring to jump the bike?

[man yells]

Yeah, with that sense of timing,
we'll never know.

When running on spring stilts,

extra speed means extra forward momentum.

[laughter]

Forward momentum and extra height
makes you less stable.

So even the slightest stumble

pushes you straight into the ground.

[laughter]

Did he mean to do that?
I don't think he did.

This road is a good, solid surface.

With purposeful, confident strides,
he loads energy into the springs.

He keeps moving to maintain his balance.

It's going well.

But when he tips too far
out of his base of support...

[yelling]

Ohh!

RICHARD: ...The released energy
of those springs sends him flying...

for a rear end shunt.

MAN: [bleep] hell!

Oh, my God!

[man laughs]

- [electricity crackling]
- [creaks]

[clattering]

RICHARD: What scientific concept

did this hardworking tow truck operator
fail to consider?

- [glass shatters]
- [electricity crackling]

The scientific concept this hardworking
tow truck operator

failed to consider is...

- MAN: [bleep]
- RICHARD: ...tension.

WOMAN: You have to be kidding me.

RICHARD: The force created
when one object pulls another.

As the tow truck winches in the chain,

tension pulls the car upright.

The impact of the car landing
detaches the chain

and all the tension vanishes.

WOMAN: [bleep] kidding me.

RICHARD: Oh, and he should
have put the handbrake on.

- [electricity crackling]
- [creaks]

Tiny David confronted
the enormous giant Goliath

with nothing but a simple sling.

Its modern-day descendant, the slingshot,

can be just as deadly,

so don't fire them
at inappropriate targets,

like people's heads.

He's taking very careful aim...

MAN [groans]: [bleep]

RICHARD: ...At entirely the wrong target.

- MAN: [bleep].
- [laughter]

RICHARD: Understanding the power
of the slingshot

is the same as understanding springs.

We need our old friend Hooke's law.

Instead of compressing springs,

this time we're stretching rubber.

When elastic is stretched and made taut,

it stores elastic potential energy.

In physics, they define
that stretching as work.

Double your stretch and you quadruple
the potential energy.

As you let go,
potential energy is transformed

into kinetic energy.

And you thought it was just a stick

with a piece of elastic attached to it.

Well, it is, but those sticks can be big.

Remember, when elastic stretches,
it's storing energy.

[man screams]

So the work he's put in has returned...

to hit him in the chest.

The line between success
and failure can be...

BOY: Ow, my foot.

RICHARD: ...Well, elastic.

These guys are attached
to a giant human slingshot.

Energy from the quad bike
is doing all the work.

[woman screams]

RICHARD: If these guys
weren't strapped in, they'd go flying.

But as they are strapped in,
the kinetic energy is transferred

back into the elastic,

and it rebounds them
in the other direction

at about 60 feet in 1.6 seconds.

That's almost 25 miles per hour.

I know, who knew the potential fun
of so much energy?

Instead of flying off at an angle,

this couple are going straight up.

MAN: Holy smoke!

RICHARD: Potential energy is transformed
into kinetic energy.

MAN: OK, all right, all right.

RICHARD: And all his excitement
is transformed into passing out.

[laughing]

MAN: What happened?

- RICHARD: You fainted.
- MAN: OK.

MAN: Close your eyes.

RICHARD: This guy's stretching
that elastic an awful long way

and it shoots from release to impact

in just 60 milliseconds...

- [groans]
- [laughter]

...which isn't great for the n*pples.

They say all work and no play
makes you dull.

They just need something to dull the pain.

- [screams]
- Yeah.

Oh, look, they match.

MAN 1: Both of you guys go in there.

MAN 2: That is good.

RICHARD: If you've done
your sums correctly,

you'll have exactly the right amount
of potential energy

stored in the elastic to convert
into exactly the right amount

of kinetic energy when released.

Ah, no one likes a show-off.

- [electricity crackles]
- [creaks]

Our ancestors knew a thing or two

about building towers
to last hundreds of years,

the Eiffel Tower,
the Leaning Tower of Pisa,

many other towers,

but what about a human tower?

Not a monument for hundreds of years...

more like a few days in hospital.

OK, so the human body
is not as strong as stone,

especially not mine,

so it's really not advisable
to try and build a human tower

if you don't want to break any bones.

One of the strongest shaped structures
is a pyramid.

Like bricks in a wall,
the best way of stacking humans

is to have each overlapping
two people below,

which distributes the weight
across and down

as evenly as possible,

with the lightest people at the top

and the strongest and heaviest
at the bottom,

holding the most weight.

Some cultures around the world
have time-honored traditions

of building human towers at festivals.

Isn't that a beer festival?

Instead of putting
the strongest bodies in the base,

those two big lads are on the top.

The bricks of that tower
aren't overlapping...

and it's fallen over.

Now, that's what I call a tower.

Watch out for the cables.

This tower in Thailand goes up well.

Heaviest at the bottom,
lightest at the top.

But with no layers overlapping
to spread the load...

it collapses vertically down.

In Spain, this human tower
is called a castell.

It has a wide, strong base,
topped by a tall, narrow tower.

Those layers aren't overlapping.

Some of those poor hombres
could have over a quarter of a ton

of weight on their shoulders.

Oh, no, not anymore.

Oh, look, now it's more like a pyramid.

Because they have a low center of gravity,

short, broad towers are more stable

than tall, slender towers,

which can collapse
with just one small mistake.

Now, this tower looks stronger.

Surely three people
on each layer of the tower

should be better than two
to spread the load.

No, they're still not overlapping.

Reportedly, the highest human tower ever

was over 40 feet high.

That one's, well, maybe 25 feet.

Oh, no, now it's only 10 feet.

Olé.

- [glass shatters]
- [electricity crackling]

I personally very much enjoy watching

adults and children
thrashing at small objects

with pieces of metal.

But don't worry.

[laughter]

Yes, I'm talking about golf.

A great golf swing relies on using
the double pendulum effect.

The first pendulum
is from the shoulders to the wrists.

The second pendulum is the hands and club.

Together, this creates
more acceleration in the club head.

The faster your club head is going
when it hits the ball,

the more kinetic energy
will be transferred

and the further the ball will travel.

I think my double pendulum
needs more practice.

He's very trusting.

Does he know professional golfers

can achieve a club head speed
of over 120 miles an hour?

I don't think he did.

[laughter]

Momentum is transferred
from the club into the object it strikes.

The highest amount of energy transferred
from a golfer's body to his club

during the swing is five kilowatts.

Some lawnmowers only need one.

I don't know what they're doing,
by the way, or why.

Tiger Woods once hit
a golf ball 498 yards.

That's about 497 yards
further than he's managed.

[laughter]

If the club doesn't hit the ball,

all the momentum and energy
is retained in the club.

[man laughs]

[continues laughing]

That can't be a good idea,
no solid stance.

And if it hit the ball,

he might have transferred
some of that momentum onto it.

Maybe he just needed a longer club.

The best way to get good at sports
is to start them early.

MAN: Where is that going?

RICHARD: Gives you time to improve.

Lesson one for the kids,
if you swing twice as fast,

you need four times more centripetal force

to keep hold of your club.

Less like a tee off,
more like time for tea.

[laughter]

- [electricity crackling]
- [creaks]

When they grow tired
of surfing the sidewalk,

skateboarders often turn to grinding.

It's not rude, it's just sliding the board
along a rail.

Of course, aiming high
brings many skaters down low.

MAN: Ow!

RICHARD: If you're one
of those people who think

that low-slung pants
are a sign of low achievement,

then you are missing the fact

that high end skateboarding
requires an instinctive grasp

of classical mechanics,

because skating is all about
center of gravity and momentum.

And low slung pants.

Here's how to grind with success.

A clean landing with the board
on the rails

allows the skater to keep control
of his body's position.

The skater must lean back slightly,

to counteract the force of friction

that tends to tip him forward
off the board.

For a good exit,
he and the wheels should land

in the direction of travel.

Even if you don't know your board slide

from your laser flip...

[whispering] I do, I do, I don't.

...you can admire the triumph
of hope over experience

of these hardy skate experimenters.

This dude is trying a Smith grind,
or is it a 50-50?

He's supposed to maintain perfect balance.

It's called a 50-50
because it's meant to be on both tracks,

not because those are chances
of him smashing his face

on the concrete.

MAN: Oh, [bleep]

I hurt my head...

RICHARD: You did.

MAN: ...and my wrist is broken.

RICHARD: Probably.

I know skaters
are supposed to be laid back,

but this guy's laid out cold.

His center of gravity
is just too far backwards.

Longer board, specially built rail,

this should be easier.

CROWD: Ohh!

RICHARD: Easier to bail.

That'll teach him to keep
his board beneath him.

That looks like a cool rail to grind.

But no trick is worth losing teeth over.

He appears to have ground
further on his bare skin

than on the board.

Don't try this at home,
or you could be eating ice cream

through a straw for weeks,

which gets boring.

MAN: Dude, your whole [bleep] face.

RICHARD: It doesn't matter
how high your rail

or how low slung your pants,

misplace your center of gravity,

and you end up with a bum deal.

[laughter]

That was good.

A perfectly balanced grind.

Not happy to have done it just once,
he's going for an encore.

His velocity's right,

his center of gravity
is in the right place,

but his wheels haven't landed
in the direction of travel.

His second helping
leaves him chewing concrete.

[glass shatters]

[electricity crackling]

[glass shatters]

Yes, we've made it
through another cavalcade

of catastrophe and c*ck-up.

If, after all the pain and destruction
you've witnessed,

you're still contemplating similar stunts,

think first about observing
the laws of science,

not the Science of Stupid.

[lively fiddle music playing]

[man screams]

[inaudible]

MAN: Ohh!