05x03 - ba*ls, Bungee Jumping and Tether Ball

[bunniefuu]

[Dallas] This is the Science of Stupid.

Yes, this is the show where we pull up the
rubber gloves of science,

and sit through great
piles of stupidity.

We learn the fun way.

While others
learn the hard way.

Then we reveal
what went wrong.

And why.

It might be they've misunderstood
moment of inertia.

It could be they didn't consider
kinaesthetic awareness.

Or maybe they'd
forgotten all about torque.

But luckily, we haven't.

So don't try any
of this yourself.

Watch out.

It's the Science of Stupid.

In this show
we'll be looking at.

Phases of matter.

Centripetal force.

And transfer of momentum.

But first this.

I read somewhere, that the secret of
staying young looking is some quick

facial exercises, followed by a little
cold air to tighten the pores.

So I thought I'd give it a go.

[screams]

[Dallas] The things
I do to keep looking this good.

Yes, thrill seekers have found a myriad of
inventive ways to use elastic cord.

From lake launchers.

To snowboarding!

Where physics meets pain!

You see what I mean?

That is gonna
smart in the morning!

But maybe the bungee cord is best used
for its intended purpose.

Precision bungee jumps are all about
stopping just before you hit something.

So if you're thinking of giving one a go,
then you really, really,

need to understand
the science.

As our man jumps, he starts to accelerate
downwards, due to gravity.

After the cord becomes taught, he applies
stress to it, and it exhibits strain as it

stretches elastically.

The amount of strain is determined by the
cord's Young's modulus,

or how stretchy it is.

As long as the stress doesn't
exceed the cord's strength.

Get it wrong,

and our man's
in for a bad time.

So it's all about stress, strain and
knowing your Young's modulus.

I had no idea that jump masters had to
have such a firm grip on physics.

[man] Big smile mate.

[man] Let's get bungee jumping.

[Dallas] This guy is jumping 160 feet
and wants the cord to bounce him

back, just before
he hits the lake.

-[man] I'm scared.
-[Dallas] I'd be nervous too.

Your life is in the hands of someone who
wears a baseball cap to work.

[man] Jumping!

[screams]

[Dallas] My words exactly.

The jump master messed up his static
weight, Young's modulus calculation.

So our jumper.

Got a soaking.

If you're thinking of trying
home made bungee,

it goes without saying
that you really

need to start small, especially if maths
isn't your subject.

[man] Ooh.

[Dallas]
Or anatomy.

[man] Yeah.

[Dallas] The stress created by this
guy's weight and his fall,

ultimately exceeded the
tensile strength of his setup.

[man] Ooh.

[Dallas] Well he seems happy enough.

[man] Why?

[Dallas] This lucky guy's friends have
organized a surprise for his stag do.

[man] What are you doing?

Why are you blindfolded?

[man] I'm bungee jumping.

[man] Blindfolded.

[Dallas] That
should make it a lot less scary.

[man] Where?

[man] Who knows?

[Dallas] So, as long as your jump
master knows his maths,

you should be able to jump
with your dignity intact.

[man] One, two, three go.

[man] Oh.

[Dallas] As long as none of
his friends are involved.

[man] Oh come on.

You know it's tough being a fan of
my local football team.

I've known teabags to stay in the cup
longer than we usually manage.

But that hasn't dulled my love
of the beautiful game,

the poetry of the ball in motion,

the grace of a
well timed move.

But most of all,
I love a trick shot.

[man] You good?

[man] Yeah.

[Dallas]
Lovely stuff.

To get these skills
takes hours of practice.

[man, off-screen] Oh pickle.

[Dallas]
Which he hasn't done.

But these guys have.

Nice moves, good
strike, back of the.

Head.

They weren't trying to do headers, which
is a shame as they are vital to the modern

game of football.

So we'd better find out the
science behind this skill.

As these footballers pass the ball,
there's a transfer of momentum between

the ball and their heads.

The ball compresses, storing
elastic potential energy.

Then rebounds
releasing this energy.

Because the ball has a
much lower mass than they do,

it experiences a
larger change in velocity.

But the players still need to
tense their neck muscles

to absorb the
momentum safely,

without their heads
being snapped back.

Anyone who's ever given this
a go will tell you,

that the angle the
ball bounces off is

very sensitive to the relative
position of ball and head.

So let's start with
a few dos and don'ts.

Firstly, do check the
ball's regulation size.

[man] Ball...
[bleep]

[Dallas] Yeah, that one's a bit big.

The larger heavier ball, has a bit too
much momentum for him to absorb well.

So he doesn't.

But he was fine
after a little sit down.

Always call for the ball.

So that doesn't happen.

When you're concentrating on
getting the correct position

for the header's launch angle,

it's hard to maintain
awareness of your surroundings.

Which can be painful.

And always practice
somewhere with enough space.

Or no amount of neck
tensing will help you out.

ba*ls are good at storing and releasing
elastic potential energy.

Whereas furniture
is less good.

And when you've mastered all of that,
you can use your new skills for

all sorts of things.

Like finding a shortcut
home from the pub.

[man] I'll be honest,
that hurt a little bit.

[Dallas]
Remember, don't drink and dive.

I think we all enjoy a bit
of early morning gymnastics.

But what scientific principle is this
indoor acrobat about to show us?

[Dallas] We asked
what scientific principle

this flexible fellow
was about to demonstrate.

Yes it was torque.

As the acrobat pulls himself
into a handstand,

his center of mass
doesn't come to rest

directly over his hands,
and his weight generates

a torque that
tips him backwards.

Which gives his friend the sort of wake
up, that even a triple espresso would

struggle to match.

Nowadays it seems that
everyone has an arch enemy.

Sherlock Holmes has Moriarty, Batman has
the Joker, and Harry Potter has Voldemort.

And I've got a nemesis
of my very own, kerbs.

They're one of the things us
skaters have to watch out for.

Along with changes
in road surface.

Turning too sharply.

And pretty much
everything else.

Yes, skateboards are very dangerous,

especially if you are trying
to do something

silly on them,
like go downhill.

And science tells us why.

On a smooth hard surface,

a skateboard's wheels experience minimal
rolling resistance,

so you build up speed quickly.

He needs to lean forwards
to stay in control.

But if a sudden change in surface
increases rolling resistance,

he's perfectly positioned
to separate from the board.

Add to that, an accidental lean will make
the board turn sharply.

Yes we can thank the wheel and its low
rolling resistance for these

nail biting downhill speeds.

In fact the fastest speed achieved
standing on a skateboard is almost



But it also means that when things do go
wrong, it happens quickly.

Sometimes very quickly.

Like that.

He turns too sharply and
the rear wheels stop turning.

Their rolling resistance is replaced by
frictional resistance, which is higher,

so his board slows down,
a little bit faster than him.

It's probably wise
not to go too fast.

And to avoid bumps.

He handles the rolling resistance changes
well, but when he hits that divot,

the board stops dead.

And his face gets some
unexpected exfoliation.

This looks a bit
less dangerous.

Slope not too steep.

Nice, gradual acceleration.

And look how relaxed that guy looks, he's
just casually texting.

[man] Oh, [bleep].

[Dallas] Ooh which now seems
like an obvious mistake.

Put it away, Jones.

Thank you.

Yes it's time for
today's science lesson.

That part of the show, where we take apart
one specific scientific principle to see

how it works.

So who can tell me what the
following have in common?

This glamorous sunbather.

[screams]

[Dallas] This
hapless charity fundraiser.

And this brave
field researcher.

The things people will
do in the name of science.

Truly inspirational.

Did you guess that they were all to do
with the phases of matter?

Well don't feel
too bad if not.

That was a tough one.

Matter can fall into a number of different
categories with differing characteristics.

But the ones we're most familiar with are
solids, liquids and gases.

As the dry ice is poured in, its vapor
easily diffuses through the space,

changing its volume
to fill the beaker.

When we add this liquid, it flows,
changing shape to confirm to the vessel,

but not its volume.

This is because the molecules have less
kinetic energy than those in a gas.

The beaker is
of course a solid.

Its molecules are tightly held together
and can't change shape easily.

Unlike liquid or gas,
solids can be brittle.

There is another type of matter we
occasionally see here on earth.

And that is plasma.

It's usually created when energy is added
to a gas, so that electrons break fee of

their atoms.

So let's see who's
been paying attention.

Question one, do gases or liquids have
stronger molecular forces?

[man, off-screen] Asher dive!

[Dallas] That's right it's liquids.

[woman, off-screen]
Are you alright?

[Dallas] Air is
a gas so can change its volume.

Whereas liquid water has a fixed volume
and is bound together by stronger

molecular forces,
so it's less compliant.

And hurts more.

[man, off-screen] Asher,
you're bad at diving!

[Dallas] This guy is trying to jump
through a gas into a liquid.

And he kind of manages it.

But his face hits the seesaw, which is a
solid with fixed volume

and bound by stronger molecular forces,
which makes it a lot less yielding.

And a lot more hurting.

Question two.

Do all solids
act the same way?

This lady is about to show us.

[man, off-screen] Matthew has no
idea we're about to do this.

[Dallas] Don't try this at home,
because as we can see,

some solids like rubber,
can stretch into form,

allowing the water inside to
change shape to some extent.

But the ground can't do this,
and neither can Matthew.

Luckily he was okay.

The ice here is a solid, which
allows him to slide

on top of it like this, which is cool.

And this.

Which is a
different kind of cool.

Ice is a brittle solid.

Now the force of his fall was large enough
to make it fracture.

And those shorts suddenly
seem like a really bad choice.

Okay, last question.

What happens when you add
even more energy to a gas?

That's right, you get
a plasma like lightening.

It's formed when an electrical discharge
from a thunderstorm has enough

energy to temporarily free
electrons from their atoms.

And remember, water
conducts electricity.

So that's phases of matter.

Useful for surfers,
and water skiers.

[man, off-screen] Hey, stop the car!

Oh my God,
are you kidding me?

I've recently discovered the
sport of tetherball.

It's a bit like volleyball without the
worry that one of your team mates will

accidentally spike the ball
into the back of your head.

I like to think of it as a
pain free way to enjoy my hobby.

Hang on, that looks familiar.

And that.

Maybe you'd be safer using
the pole for something else.

[woman, off-screen] No!

[Dallas]
Much better.

The aim of tetherball is to get the ball
past your opponent enough times that it

completely wraps
around the pole.

And a few tips from science
should make that a lot easier.

As the player hits the ball it quickly
reaches the limit of the rope,

and centripetal force makes
it travel in a circular path.

But as the rope wraps around the pole, its
angular velocity can subtly increase.

And it's harder to predict when there's a
vertical component to its path,

so hitting it upwards
is a winning technique.

So there we go
those are the basics.

We all knew that.

But I think we're
ready for a masterclass.

[man] Today I'll be
doing a little tetherball...

...with my sister.

[Dallas] He sounds like quite the
expert, so this should be good.

How wrong can you be.

If you hit the ball with the side of your
fist, you can get more power

and are less
likely to get injured.

Unless you follow through and
smack yourself in the face.

For a good game of tetherball, you want
both players to be fairly evenly matched.

And these two are.

They are both rubbish.

The first girl adds a significant vertical
component to her shot,

so its trajectory
was less predictable.

And then she was laughing so
much, she failed to block it.

I'm not sure who's winning here, but it's
definitely not the sport of tetherball.

Maybe this guy
will do a bit better.

It certainly seems
to be a heated game.

It's like watching an
allegory of my life.

As he throws the ball it quickly reaches

the limit of the rope
and centripetal force

pulls it around the pole.

But he's given it so much angular
velocity, That it arrives back where he's

standing quicker than
he can get out of the way.

Helpless, vulnerable, naive.

Yeah maybe the tagline on my Internet
dating profile does need a bit of work.

But coincidentally all of
those phrases

could be used to describe
babies needing a lot

of help to make
it into adulthood.

Like this foal.

No wonder she's
got a long face.

They say all a good
mother needs is love.

But I think there's probably
a bit more to it than that.

Check he's alright then.

Just recently, I've been wondering what it
is that makes a good parent.

Luckily when it comes to
the animal kingdom at least,

science has some answers.

Not all species
require parenting.

On the whole for animals who have
offspring in the dozens or even thousands,

there's little to no
parental investment.

But for animals that have offspring in
small numbers, the level of

parental investment is generally higher,
and can last many years,

until the offspring has
matured, and learnt enough

to be able to
survive independently.

And it tends to be the
more intelligent the animal,

the longer the period
of parenting required.

As we all know, parents
need to lead by example.

As in many species babies will mimic and
replicate, many behavioral patterns

they see and hear.

So let's watch some
classic parenting in action.

This mum certainly looks like she's got
it all under control.

Scaredy cats.

When this mother loses control, it
triggers a stress response in her kittens.

The other way animals learn
is by experimenting

in a safe and
controlled environment.

Elephants tend to have one baby at a time,

and males will stay within
the family group

until they reach maturity
at around 12 years old.

This mother is letting her baby practice
the behavioral responses he'll need,

if there's a real threat.

But just like all toddlers, when things
don't go his way, he appears to have a

bit of a tantrum.

I'm exactly the same.

[man, off-screen] That guy is
not messing around.

We humans are massive suckers when
it comes to babies.

And not just of
our own species.

Because of something called
baby schema,

we're genetically
programmed to be charmed by

he young of lots
of other animals.

Like this gorgeous baby owl.

Isn't nature wonderful.

Naturism.

Well that's a bit
more polarizing.

Erwin Schrodinger once said, "I don't like
it and I'm sorry that I had

anything to do with it".

He was of course talking about quantum
theory but,

I have a feeling several of our

experimenters feel
exactly the same way.

[music plays through credits]