03x13 - Springboard, Low Rider and Mud

[bunniefuu]

[Richard]
This is the Science of Stupid.

-[electricity crackling]
-[glass shatters]

[alarm blares]

Yes, this is the show
that combines hard science

with utter stupidity.

Watch as one of these
stunt men and women

put their lives on the line

in the name of scientific endeavor.

We'll reveal what went wrong and why.

With the help of key
scientific principles,

such as rotation, center of mass,

and that cheeky trouble maker, friction.

So watch and learn,
but please don't imitate.

Because this is the Science of Stupid.

[glass shatters]

[electricity crackling]

In this show, we'll be exploring momentum,

excess pressure,

and the sticky subject of impact force.

But first, this.

[glass shatters]

[electricity crackling]

[glass shatters]

Starting life in California
over 60 years ago,

skateboarding began
as an urban alternative to surfing.

But the more observant
amongst the skateboard community

soon realized
they didn't actually have any waves.

So they decided to make their own.

Yes, I am of course talking about ramps.

Like waves...

only much harder.

As things on land generally are.

[man groans]

[man, off-screen]
That really looked like it hurt.

[Richard] That's probably because it did.

Some do try to minimize the risk.

But with varying success.

For starters, I'd advise
using a helmet and pads

as opposed to a hedge.

Now I realize that however sensible
the don't do it option might be,

not everyone is gonna be ticking that box.

Which is all the more reason
to look carefully at the science

behind ramp jumping on a skateboard.

Having built some momentum,
he drops as he hits the ramp.

This is called pumping,

and can increase
his momentum further.

Having left the ramp,
his trajectory is determined

by his velocity and launch angle.

But he must ensure that his feet
stay above his board

so he can land on his wheels.

It all boils down
to having enough momentum,

getting your launch angle right

and staying above your board for landing.

Let's start with a small ramp,

which means you need less momentum.

But not that much less.

He's using gravity to help gain momentum.

[yelling]

Only not very well.

Not enough momentum,

and what he did have
he used to carry him over the ramp,

without his skateboard.

A steeper ramp gives more momentum.

Which, for him, is a bad thing.

That's because the wheel of his skateboard
got stuck in a crack.

Leaving his face
to make the jump without it.

Nice long approach,

not sure about the velocity.

[man] That was so perfect.

[Richard] Nothing like
having low standards.

[man] You okay, bro?

[Richard] Perhaps the answer
is a professionally built ramp.

[man, off-screen] Oh, my God.

[Richard] Or perhaps not.

Good momentum, okay trajectory,

but landing on wheels
is preferable to back.

[man] Water! Water!

[groaning]

[Richard] Thirsty work this skateboarding.

[groaning]

[electricity crackles]

[creaks]

As far as life skills go,

hopping might not strike you
as all that essential.

But try to imagine a world without it,

and you realize
just how important it really is.

There'd be no hopping over things,

hopping onto things or off things
for that matter.

No, being able to hop is a skill
that will definitely come in handy.

[woman laughs]

Especially for her.

And it's a key ingredient
of the triple jump,

sometimes called the hop, skip and...

whatever that was.

What was he hoping for?

To ensure that next time
you try and hop on a bus

you don't end up under it,

first consider ground reaction force.

Here's the science.

To launch, he must push
against the ground.

The ground exerts
an opposite reaction force,

making him take off.

And he must absorb it again when he lands.

To hop forwards, he must lean
his center of mass forward

and make small adjustments

in the trajectory of his jump
to stay upright.

By moving his base of support,
he's able to stay balanced.

I'm actually hopping at the moment,

I'm just so good you can't tell.

Now the world of hopping
is divided into two key groups.

Those who hop on one leg,
and those who hop on two.

So shall we start with
the two legged hop?

Thank you.

This boxer is practicing his hop
into the ring to create a big impact.

Oh, not quite enough height.

-[groans]
-[man laughing]

And that's not enough forward momentum.

Plus a twist, meaning the big impact
was not where he wanted it.

Before we move on to one footed hopping,

did you know the fastest time
to hop a mile on one leg

is 18 minutes and 25 seconds.

Oh, yeah, this is a real sport
with proper records and everything.

This guys is hoping
to break the world record

for hopping backwards
with a 90-kilogram weight in his mouth.

Well who hasn't dreamed
of going for that one?

The weight is moving
the combined center of mass,

so it's more of a challenge
to stay balanced.

-[clangs]
-[yelling]

Oh, well done, he's pleased,
I think he's pleased.

[man] I did it!

[Richard] He's pleased.

And of course hopping is fundamental

to the serious sport of hop scotch.

[woman] Now what do I do first?

[Richard] Uh, you hop?

That's it.

[girl screams]

Poor grandma didn't hop high enough

so caught her toe and rotated down.

Hop scotch may take a life time to master,

but it is really for eight years olds.

But no one loves hopping more than people

from the world of Latvian folk dancing.

Oh, dear.

Two feet spreads out the force.

One foot concentrates it.

Which is not good
on a poorly constructed stage.

Still, you know what they say,
the show must go on.

And what a show it is.

[electricity crackles]

[clattering]

Can you guess what scientific principle

this young scientist is going to show us?

[glass shatters]

[electricity crackling]

So any ideas what area of science
he's about to explore?

Could it be wind force?

[screams]

Oh, no, its kinetic energy.

The speed of the fan
gives the latex glove kinetic energy.

Which he then absorbs.

I'd stick to magnets
for your next experiment.

[electricity crackles]

[creaks]

Picture the scene, you're at the pool,

you saunter up to the diving board
looking pretty damn hot.

Certainly everyone's happy to see you,

why else would they be laughing?

All you need to do now is wow them
with a memorable dive.

[man] Yo.

[Richard] Um, that's not really
a diving board.

Oh, but it was memorable.

Let's try it with a diving board.

No, that's a table.

That's a bit better.

Now for that perfect dive.

[yells]

That wasn't what I had in mind.

No, what you need
for a really impressive dive

is a springboard with plenty of bounce,

so as to launch you gracefully
into the air like a swallow.

That was more free falling turkey.

Obviously this springboard thing
needs a bit more work.

So shall we see what science
has to say on the subject?

He starts the dive by pushing down
on the board

in a series of small bounces.

The springboard bends
and stores elastic potential energy

each time he lands.

When the board springs back
it gives him back kinetic energy

to give him more height for the dive.

But enough friction is crucial,

to ensure he doesn't slip when he jumps.

You see, it's all about getting
enough grip as you bounce

to get that elastic potential energy
without slipping over.

Let's see how we go.

Oh, not great.

Not enough bounce
meant not enough vertical velocity.

And virtually no horizontal velocity,

so he hit the board

with around the same momentum as a melon,

traveling at ten miles an hour.

Get enough bounce
and you can pull a few trick dives.

[people gasp]

That's not a trick I've seen before.

Good bounce but elastic potential energy
was wasted by a loose board.

I hope that sorted out your bounce.

Even so, with all that
elastic potential energy,

a slip can be all the more painful.

So you're gonna need
some help from friction.

Perhaps the secret
is to start when you're young.

Oh, no, great.

And maybe look
where you're going next time.

Some extra mass
can really help with the friction.

[laughter]

Oh, never mind.

Initial good demonstration
of elastic potential energy

but lack of friction
means center of mass

gets a playful nudge.

Along with his face.

[bell rings]

[beaker shatters]

[gurgling]

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

The part of the show
where we shine the spotlight

on a particular scientific principle.

But can you guess what it is?

Well, it's keeping him
from falling off his head.

And it's keeping him
spinning in his, uh, hoop thing.

Well, it was.

And her...

not so much.

[woman] I landed straight on this side
of my face and on my eye.

[Richard]
Yeah, I'm no doctor,

but I don't think
you want to fall on your eye.

[groans]

If you haven't guessed it,

today's theme is
the weird self-stabilizing phenomenon

known as the gyroscopic effect.

But how does it stop
some things from toppling over,

and not others?

Let's have some science and find out.

Any spinning object behaves
like a gyroscope

and will resist changes

to the orientation
of its axis of rotation.

This is because it's angular momentum

and thus it's spin direction
must be conserved.

The faster it spins
and the great the object's mass,

and the further it's distribution
from the axis of rotation,

the more stable it will become.

Even in mid-air.

You can get that gyroscopic stability
in pretty much any spinny thing.

Whether they're spinning like this
on the horizontal axis,

or like this, on the vertical axis.

Now for a test, first question.

Can you name one thing
that increases gyroscopic stability?

It's spin speed.

[laughter]

He built up good speed at first,

but he leant too far and slowed down,

decreasing the gyroscopic effect

as well as his job prospects.

Here's the same effect
with the horizontal axis of rotation.

Fast spinning wheels and bulky tires

can actually help stabilize a motorbike.

Even when you're not on it.

[man] Go get it!

It's going to crash!

[Richard] Nah, it'll be all right.

Maybe not.

[man 1, off-screen] Oh.

[man 2, off-screen] *****!

[Richard] Question two, aside from speed,

what else A*DS that gyroscopic stability?

Well, just like he's doing,

it also helps to start
with your mass more spread out.

But not like him.

Not sure what kind of effect that is,

but it's not a gyroscopic one.

[girl, off-screen]
Yeah, do a ballet pirouette. Go on.

I want to see five.

[Richard] All right, bossy.

But fortunately, ballet dancers

can use the gyroscopic effect
to balance on their toes.

-[girl screams]
-[laughter]

He however cannot.

The spin seemed wide and fast enough,

it's just a shame
his toes weren't up to it.

-[girl screams]
-[laughter]

Question three, true or false?

The gyroscopic effect only works

when the spinning object
is in contact with the ground.

False.

The spinning motion
of this Frisbee stabilizes it in the air,

and keeps it on a level course.

-[shatters]
-[man groans]

Level to his face.

Well, maybe he shouldn't be
peeking around trees...

-[shatters]
-[man groans]

...or that's what you're going to get.

So that's your lesson
on the gyroscopic effect

and why it works for some people
but not for others.

He's one of the latter.

[electricity crackles]

[creaks]

I'm a big believer
that it's better to solve disagreements

through intelligent discourse
rather than fighting.

Well, I think that most people
would agree.

Except perhaps
when the weapons of choice

are bits of cake, pies and whipped cream.

The custard pie attack
is the classic ingredient

for any fun food fight.

Jumping out of the fridge

and shoving your friends over
is less classy.

And not so fun for him.

[laughing]

You see whilst you might think food fights
are perfectly harmless,

they can result in a fair amount of pain.

So best to check out the science.

Velocity and release angle
determine trajectory.

The lower the food's density,
the more likely it is to disintegrate

and the lower its impact force.

The heavier and harder
the food and the less air time

over which drag can slow it down,

the greater the impact force
is likely to be.

Okay, remember,
keep it fast, keep it sticky,

but bear in mind
if you're fighting at distance,

hard food might be easier to throw,

but it will hurt a touch more.

[woman, off-screen] Daddy's doing it.

[Richard] Aw, how could
you have a food fight

with a small child?

[woman, off-screen]
He's gonna throw it right to you.

Oh. [laughing]

[Richard] Oh, like that.

Spinning dough
flies well through the air,

and it's soft texture
means less impact force.

So the kid's okay
and has got a lovely new hat.

Let's reduce the distance.

This is pretty close.

[laughing]

But that was closer, touché.

Having delivered the pie,

her forward momentum
is stopped by a bin,

and then the momentum of his pie
was stopped by her face.

[man] He already came out, so...

[Richard] Let's do a comparison.

That was short range,
and that was longer range.

This chap applies force

to direct his target into the cake
for maximum accuracy.

But throwing the cake
involves implying a force

to accelerate it along the trajectory.

Not so accurate, but a wider impact area.

Shall we call it a draw?

So what happens if we make
our food less creamy

and a bit more solid?

Well...

that.

Yeah, the denser the cake,
the bigger the impact.

That was dense.

A final bit of advice,
try not to fight the food itself.

[laughter]

Hmm, his head might
have been dense, it was,

but so was the pumpkin.

Bet he dreads Halloween.

[electricity crackling]

Throughout history there are have been
some wonderfully pointless inventions.

Musical socks, pogo sticks,
jewelry for dogs,

and now there's a new one
to add to the list.

Welcome to the flyboard.

A bit like a skateboard
but attached to a high pressure hose.

With an expert it can look super cool.

But with everyone else...

it kind of doesn't.

Even if you have a version like this...

or this.

[yells]

Now I'm not sure if I'm really selling
this whole flyboard thing properly,

so let's see if science
can do a better job.

It's all about
Newton's third law of motion

which states that for every action,

there's an equal and opposite reaction.

The water's downward acceleration
is the action.

An upwards force on the board
is the reaction.

The water is pressurized by a jet ski,
which acts as a pump.

To steer, he can adjust
the angle of the water jets,

and more powerful jets
give him more height.

But if he shifts his center of mass
too far forward or backward,

gravity will rotate it
back into the water.

It would seem then that the trick here

is to balance your water pressure,

thrust angle, and center of mass.

Which sounds dangerously like
multitasking to me.

Very dangerously, actually.

Because you can get
almost 50 feet in the air

on one of these things,
which means that if you fall,

you could hit the water
at almost 40 miles an hour.

Not quite 50 foot,

but more than enough
to embarrass yourself.

I don't know about you
but waving your arms around

doesn't suggest
a well-balanced center of mass.

Now there is a logic here,

some tight rope walkers us an umbrella
to help them balance.

Ah, look at that,
it's just like Mary Poppins.

Meets the Little Mermaid.

Sudden lack of thrust
to counteract gravity,

but not enough strength
from umbrella to act as parachute.

Let's try the jet pack version.

[laughter]

Poor thrust control,
poor center of mass position

and gravity not exactly helping.

What about another hobby?

I've heard fishing has its moments.

Or collecting things.

[glass shatters]

[electricity crackling]

[glass shatters]

So everything you need
to know about the science

behind what they were doing wrong.

The philosophical question of why
they were doing it in the first place

would take considerably longer.

And probably involve the word "stupid."

So please, stay safe,

and don't copy any of the stunts
you've just seen.

Goodbye.

[woman, off-screen] Oh! [laughs]

[groans]

[yells]

[man, off-screen] Ohh!

[people gasp]

[yells]

[girl screams]