06x05 - Wake Surfing, Water Slides and Sparring

[bunniefuu]

[Dallas off-screen] This
is the Science of Stupid.

Yes.

This is the show where we mix a scoop of
science, with a whole load of stupid.

[man off-screen] Watch out,
watch out, watch out, watch out.

[Dallas off-screen] Then step
back and see what happens.

Get ready for amateur researchers
to test their limits,

answering the questions that
nobody was really asking.

Then we reveal what went wrong,

and why, with the help of such
scientific principles as

deceleration, angular
momentum, and acceleration.

In the story of nitwits versus
knowledge,

the ending is always the
same.

So, watch out, it's
the Science of Stupid .

In this show we'll be looking at
the upside of drag coefficient,

the downside of rotation,

and when you need a bit
more hydrodynamic drag.

But first this.

There comes a moment in every man's life

when he realizes he's too old for
tubing,

had it up to here with canoeing, and
finds surfing, well, a bit limiting.

So, where can you go for your
holiday water sport thrills?

Luckily, I found a new activity that
almost seems to defy physics.

[man] Okay, let's
go wake surfing.

Okay, okay, let's go.

[Dallas off-screen] Wake surfing, as
this man is so ably demonstrating,

is the laidback lovechild of
wakeboarding and surfing,

where you launch yourself off the back
of a boat, and ride the wake.

If you're here, who's driving?

Oh, no one.

It's a great way to enjoy
the water with your friends.

Unless your friend is him.

Wake surfing dates back to at
least the 1950's,

and all you need is a boat, a
board,

and an understanding of physics.

[Dallas off-screen] In wake
surfing, position is key.

Like all board sports,

you need to position yourself so your
center of mass stays over your

base of support.

But you also need to know how your angle
your board on the wake.

Too steep an angle, and our man will
pass from wake to turbulence,

which knocks him off.

But too shallow an angle, and he'll slow
down, the wave will pass him,

he will lose stability,
and then sink.

Gary Saavedra once wake surfed

for an impressive three hours


which makes it seem like
this is an easy thing to do.

[Dallas off-screen] It isn't.

As his board moves backwards
after his trick,

his center of
mass is no longer over his base

of support, and there's
only one way that can end.

Wetly.

We all know someone like this, checking
their work emails on holiday.

Yeah, no one likes that guy,

which is just another reason
to be grateful for physics.

Our workaholic starts well,
but checking that last email,

he shifts the position of the board

to the top of the wave, the wake passes
him, and he loses velocity.

Have you tried turning
it off and on again?

This guy is flying,
and now he's swimming.

This surfer's center of mass
is too far back on the board,

so when he hits the wake face,

the board hits his face.

Celebratory drinks already,
now that's a confident move.

Well, at least you can
drown your sorrows.

Staying upright on the wakeboard
is a delicate balance of forces,

but when she leans further out,

the board tilts, digs into the water,
and a rapid increase in drag

means she's going down in one.

Still, it's always less embarrassing to
fall off the board

than to fall off the boat.

Chinese martial arts originated
in the Zhou Dynasty about

two-and-a-half
thousand years ago.

Developing the series of punches
and kicks which we know today.

[Dallas off-screen] But, to develop
skills like this

takes years of
practice.

And sometimes even
that's not enough.

Now, we all know a martial
artist kick can pack a punch.

Great in competition or
when you're kicking pads,

not so great when you're
training with your friends.

So, when sparring, kicks are designed to
train the same skills

but use less force.

Let's kick off
with some science.

[Dallas off-screen] The kicker needs to
maintain their balance throughout,

maintaining friction
with the ground

so they can keep their center of mass
firmly over the base of support.

He also needs great muscle control to
accelerate his leg

but retain enough
control to hit

with minimal impact force.

When you aren't training with a
friend, you can use more power.

Momentum will be conserved
at the point of impact.

This means the target will be
accelerated backwards if not secured.

So, to kick hard you need to build
momentum for a large impact force,

but you don't want to hurt a training
partner,

so that power needs to be
controlled.

This takes concentration.

[man] Go.

[Dallas off-screen] You
need to fix your focus.

[man] Go.

[Dallas off-screen]
And your feet.

[man] Go.

[Dallas off-screen] He spins his body as
he jumps in order to maximize

his momentum, however,
his body starts to

tilt during his spin, leaving
his center of mass unsupported.

Rather than hit the
target, he hits the floor.

So, it's a good idea to check
where your kick is going to hit.

And make sure your partner
is ready,

because if you kick your
sparring partner in the head,

it's gonna be hard to
find anyone to train with.

Unless of course,
you're related to them.

-[man] What are you doing?
-[girl] Kick it.

[man] What? You sure?

[girl] Do it, you little sissy.

-[man] You sure?
-[girl] Yes.

[Dallas off-screen] When Muhammed Ali
said, 'Float like a butterfly...'

[man] Alright, here we go.

[Dallas off-screen] That
isn't really what he meant.

When dad here makes contact, his
momentum is conserved,

and because his
daughter is so light

and movable, the impact force
accelerates her legs at more than 6G.

Luckily for them, my grandmother had a
saying, the family that kicks together,

ends up on the floor
in pain together.

-[man] You okay?
-[girl] Yeah.

[man] Table.

[Dallas off-screen]
Ah, I love Christmas,

and this guy's almost
finished decorating the tree.

Just the angel to go.

[man] Don't fall!
Thank you.

[Dallas off-screen] But, what force is
he about to unwittingly show us?

[man] I hear it cracking!

[man] Don't fall!

[Dallas off-screen] We asked you what
force this festive decorator

was about to demonstrate.

[man] I hear it cracking!

[woman off-screen] Oh my God.

[Dallas off-screen] Yup,
it's flexural strength.

Flexural strength measures how much
force an object can take when applied

perpendicular to its length.

Here, this dad and his son apply their
weight to the chair and the table.

These downward forces combined exceed
the table's flexural strength.

[man off-screen] I
hear it cracking.

[Dallas off-screen] Making Santa sad,
and giving us a very clear example

of why you shouldn't
do this yourself.

[woman off-screen]
Hey, you okay?

[Dallas] There's nothing more refreshing
than a quick dip in the pool.

And if you're looking for quick,

there's really nothing speedier than the
waterslide.

[Dallas off-screen] And that's true
whether you're more

interested in style
and grace,

or just want to
make a big splash.

But, while it may seem like child's
play,

there are many pitfalls and perils
to the humble waterslide.

So, before you put your cossie on,

make sure you've dipped your toe into
the science.

[Dallas off-screen] Slides are angled so
that the rider

can be accelerated by
gravity.

Their smooth surface is lubricated by
flowing water,

which reduces friction
between the person and the slide.

Meaning our man can build
up lots of momentum.

The pool at the bottom can slow our
rider with hydrodynamic drag.

But on impact, if he keeps his underside
smooth and his legs above the water,

then he'll minimize this hydrodynamic
drag, and maintain his speed for longer.

So, if you want to go fast, you need to
balance momentum,

friction, and
hydrodynamic drag.

Now, we've skimmed the science, let's
see how our researchers get on.

[man] It's not how it works.

[Dallas off-screen] Ah, clever.
Our first team of scientists are using

a double ring, which should
increase the speed.

[man] Oh my God, my butt.

[Dallas off-screen] And,
one would assume, the fun.

[man] Ow!

[man] My butt!

Oh my god, my butt.
Ow, ow, ow.

[Dallas off-screen] Yeah, as long as
they don't sink

too far into those ring
holes.

Still, with that low coefficient
of friction,

at least it'll be over
quickly.

Maybe that float was a mistake.

The pool at the bottom should have
decreased their velocity

by increasing
drag, however,

since the passenger at the back
of the float was larger.

[man] [Bleep].

[Dallas off-screen] The float
entered the water at an angle,

reducing drag
for a longer ride.

More bad news for that backside.

This is lovely stuff.

Plenty of lubrication, nice momentum,
and a good clean dismount.

But there's one thing
you've got wrong.

Never stand at the
bottom of a waterslide.

Our slider did well, but his friend had
higher momentum, a better body position,

and a flatter bottom, which meant he was
able to skim the surface further.

And ultimately look cooler.

But not as cool as this guy.

Obviously.

Right, quiet please, I hope you've all
got your notepads at the ready,

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

The bit of the show where we dissect one
particular principle

using the scalpel
of science.

So, what have these
three got in common?

[Dallas off-screen] This
indecisive parachutist.

Well, I hope he's a parachutist.

This tree climbing
chain reaction.

[man] [Bleep].

[man off-screen] Uh, I
kind of got that on video.

[Dallas off-screen] And this groom, who
really does need better friends.

Yes, of course, I'm sure you all guessed
that they were examples of

gravitational potential
energy, or GPE.

That's of course a type of potential
energy

whose presence is only felt once
it's converted

to another form of energy.

[Dallas off-screen] Fruit
raised above the Earth has GPE.

As it falls towards the Earth, that GPE
is converted into kinetic energy.

And the higher the object is,
or the more mass it has,

the more GPE that's available to be

converted into kinetic energy,
the faster it will fall,

and the more energy it
will dissipate on impact.

That was fun. Right, let's see who's
been paying attention

with a little pop
quiz.

Question one, how can you give an object
gravitational potential energy?

[Dallas off-screen] That's right, by
lifting it above the Earth.

Give him a big hand.

And now give him a big hand up.

As he's raised higher by the
crane, his GPE increases.

As he moves forward,
it remains the same.

But when the rope gives out, that
potential energy

is converted into
kinetic energy,

and he hits the ground at
nearly 20 miles an hour.

Question two, what type of energy is GPE
usually converted to

when an object is released?

[Dallas off-screen] If you said,
'Kinetic energy,' you are correct.

Something to be wary of when you're
moving your favorite chair.

Or your favorite friend.

Although the drop between the roof and
the people below is relatively small,

the armchair's large mass means
it has quite a lot of GPE.

When it's dropped, this is converted to
quite a lot of kinetic energy,

which is transferred from
the chair to the catcher.

Leaving him with his feet
up, but his face down.

He'll be fine after
a little sit down.

Anyone got a chair?

And now for our third
and final question.

What eventually happens to the
gravitational potential energy

an object had?

Listen up, and you'll
get a bit of a clue.

[man] Ow!

[Dallas off-screen] Yes, it's dissipated
as other forms of energy,

like that thudding sound.

Which should serve as a warning
about trying this yourself.

So, that's gravitational
potential energy.

[boy] I'm gonna prank my dad.

[Dallas off-screen]
Is that a prank?

I think that's for the courts to
decide, we just do the science.

[Dallas] Any fool who's ever been
in love will tell you that

you don't need to be able to see
something to know that it exists.

[Dallas off-screen]
Like wind, for example.

It might be invisible, but we can see
its effects from uprooted trees.

To ruined concerts.

Wind is all around us, and yet we rarely
think about the how's and whys.

Simply put, wind is the flow
of air in the atmosphere.

Let's get a blow by blow of
the science behind it all.

[Dallas off-screen] Wind is
caused by pressure gradients.

Warm air is less dense, so
rises, causes low pressure.

Cold air is more dense, so falls, and
rushes in to fill the gap.

Although wind is invisible,
its effects are noticed when

it imparts kinetic
energy onto objects.

Its effect on these objects

will be dependent on how fast the wind
is blowing,

as well as their weight,
drag coefficient, and area.

So, wind is just air following
the rules of physics.

And if you want to avoid getting blown
over,

then your size, shape, and
density,

are all important
when facing the wind.

Easy breezy.

[Dallas off-screen] Ah, some
father and son bonding time.

That's the great thing about dads,
they've always got your back.

Well, almost always.

The sizable flat fabric of the kite has
a large drag coefficient and area,

so it acts like a sail,
providing both lift and drag.

The wind imparts a massive amount of
kinetic energy to the kite very quickly,

giving this kid a
mouthful of potato field.

These two are heading home and out of
the wind before it picks up.

Too late.

This little girl had small enough drag
to walk through the wind,

but when she went to go inside,

the large surface area of the
door increased both the area and

the drag coefficient,
sending her flying.

Don't worry, she was fine.

These ice fishermen are hoping to get
some shelter from the wind,

but the wind doesn't
like to be mocked.

Alright, here's one
for you fact fans.

There are volcanoes on every single
continent of the world,

even in Antarctica.

In fact, one in 20 people lives within
the danger range of an active volcano.

[Dallas off-screen] Lava can
reach 2,280 degrees Fahrenheit,

so this guy should
really just run away.

He's awfully confident
for a man wearing shorts.

Fashion in the
face of adversity.

This chap has sensibly got a bit of
protection,

but you still don't want to
get splashed.

Yes, I would run away very fast.

There you go.

Given the remote, but very real, threat
of lava,

how do you maintain constant
vigilance?

Well, how about with a game.

[woman] The floor is lava!

[Dallas off-screen] Where you have five
seconds to get yourself off the floor.

You're lucky, this time
it was just a drill.

The rules of this
game are very simple.

When someone says, 'The floor is lava,'
then you have five seconds

to find refuge on
a raised surface.

You can jump anywhere, but here
are a few tips from an expert.

[Dallas off-screen] Jumping onto any
objects requires both vertical

and horizontal momentum.

Make sure you land somewhere
with enough stability.

Any object not securely attached
to the ground can be unstable.

And watch out for friction.

A low coefficient of friction can mean a
slip, a fall, and you losing the game.

The rest is just
a matter of style.

Right, so, remember, stability,
momentum,

and friction, and you'll be
fine.

Sound simple enough?

Well, let's see how our
experimenters get on.

[man] The floor is lava! The floor is
lava!

-[Dallas] There's a real skill
-[man] Five, four, three, two, one!

[Dallas off-screen] in making these
things look this complicated

[Dallas off-screen] The issue here was
too much horizontal momentum,

and an incredibly
unstable landing spot.

Let's see if this
guy does any better.

[Jan] ...brown, red or... hey,
there's a color called...

...the floor is lava!

-[man] Oh, Jan.
-[Dallas off-screen] What a great way

to liven up a dull shopping trip.

But some people just aren't
that good in an emergency.

Our panicked player jumps on a roll of
carpet, and perhaps predictably,

his momentum causes
the carpet to rotate.

At least the worst he'll get
in this case is carpet burn.

Her again.

I wonder if she's
learnt from last time.

[man] The floor is lava!

[woman] Not now.

[Dallas off-screen]
Apparently not.

This time the bin is sturdy enough to
take her weight,

but unfortunately
there's a low

coefficient of friction between her foot
and the bin's edge,

so she takes a
tumble into the trash.

And I think what we've learned from all
of this, is we're totally unprepared

for volcanoes.

Well, I think that is quite enough
physics and face plants for now.

Please don't anything
you've just seen at home.

And here's a quick
reminder of why.

[man] Ready? Go!