07x05 - Horses, Tides and Model Aircraft

[bunniefuu]

[Dallas Campbell]
This is the Science of Stupid.

[klaxon blaring]

Yes!

This is the show where we draw
scientific enlightenment

from abject stupidity.

[girl screams]

[Dallas] Behold the actions
of the untrained

-and unwitting...
-[man yells]

[Dallas] ...as they risk life and limb

-[man screams]
-[woman] Oh!

[Dallas] ...in the name
of further education.

We'll reveal what went wrong

and why

through fascinating
scientific principles like...

-[glass shatters]
-[man screams]

[Dallas] ...thermal expansion...

-[expl*si*n booms]
-...electrical currents...

and the always delightful
coefficient of friction.

Mess with physics and it'll mess you up.

So watch out...

it's the Science of Stupid.

[electricity crackling]

-In this show, we'll explore...
-[woman] [screams]

[Dallas] ...the trouble with tidal
range,

the complications of...

a combined center of mass,

and the joys of momentum.

Tasty stuff.

But first, this.

[glass shatters]

[electricity crackling]

[glass shatters]

Aeroplanes are
notoriously expensive to buy.

Fortunately, their
radio-controlled little cousins

give even the likes of you
and I the chance to delight

in the science of flight.

But, even so, it can still be
quite expensive.

The key is avoiding things...

like people...

and... the ground,

and, of course...

yes, sharks.

-[man, off-screen] Oh!
-[laughing]

[Dallas] They really do get everywhere.

Clearly, if you don't master your turns,

you're gonna be spending
an awful lot of money on glue.

If you want to avoid that,
then you are in luck,

because here is the science

of steering a radio-controlled plane.

It's all a matter of perspective.

Our man has a different
perspective to the plane,

so he constantly makes judgments
about its position

and velocity to estimate its trajectory.

It's easiest when the plane
is flying away from him,

as most movements to the stick

relate directly to the same movement
in the plane.

But the reverse is true

when the plane is flying towards him.

For example, move the stick right
and the plane steers left...

and that is confusing.

[man yelps]

[groans]

[Dallas] Right, so if you remember
that while flying away,

left is left and right is right

but, coming back,

left is right and right is left,

then everything should be fine.

So it's chocks away,
and good luck out there, chaps.

[man] Throttle's full, choke is closed.

[Dallas] These wing commanders are
serious.

Their plane even has a pilot, bless.

[man, off-screen] Ah, professional.

[Dallas] And its landing gear works
like the real thing.

Must be worth a fortune.

[man, off-screen] Low pass!

[men] Oh!

Hit a helicopter.

[Dallas] It's not worth so much now.

The plane is flying
across the guy controlling it,

so it's trickier to estimate
its trajectory

and avoid the toy helicopter.

[men] Oh!

[Dallas] Don't worry, the pilot was fine

once they'd glued his head back on.

Ah, the wide-open skies of Australia.

Not quite wide-open enough.

The plane starts behind the pilot
and flies across him,

making it hard to estimate distance
and determine trajectory.

I mean, honestly, who put that tree there?

Now, what was it I have to remember
when flying the plane towards me?

Yeah, everything is...

[man] Ah!

[Dallas] ...backwards.

[electricity crackling]

[creaking, clanging]

My dear late grandfather

was very fond of the old proverb,

"You can lead a horse to water,
but you can't make it drink."

What he failed to mention was
the horse can make you drink.

Whether it's a gentle trot
through the woods...

[woman screams]

[gasps]

[Dallas] ...or an amble around
your local showground...

[woman screams]

[Dallas] ...it's thirsty work.

It does seem our equine companions

are either not overly fond of water

or they simply find dunking their riders

absolutely hilarious.

So for the purposes
of remaining in the saddle,

staying dry and ridicule-free,

here's the science
behind riding through water.

To stay in the saddle,
the rider must ensure

that her center of mass
remains as close as possible

over the horse's center of mass.

That can get trickier
when riding fast through water.

As hydrodynamic drag slows the horse,

the rider must brace herself

to prevent her linear momentum
carrying her forwards

as a result of conversation of momentum.

To sum up, race in too deep, too fast,

and hydrodynamic drag
will slam on the brakes

before linear momentum sends you flying.

It's tricky stuff,

so let's start with something simple.

Huge horse, tiny stream.
This should be a dawdle.

[woman, off-screen]
Really shorten your reins,

so she's got no choice but to cross.

[Dallas] I don't know, I wouldn't want
to annoy that horse.

[woman, off-screen] Gallop her at it.

[Dallas] I'm not sure
that's a good idea either.

[woman clicks tongue]

-[horse neighs]
-[woman screams]

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

[Dallas] All that compassion,
it just melts your heart.

She persuades the horse to jump

but gets hit in the face by some branches

and fails to adjust her center of mass.

-[horse neighs]
-[woman screams]

[woman, off-screen] Oh!

Thank you, Robyn!

[laughs]

[Dallas] So no broken bones...

[woman] I'm fine.

[Dallas] Just a slightly
fractured friendship.

This horse seems a little braver.

[woman, off-screen]
I think she might do a big one.

[woman] Oh no!

That was a bit unfortunate.

[Dallas] Hmm, someone's got
the knack of understatement.

As the horse enters the water,

hydrodynamic drag causes it
to decelerate...

but conservation of momentum...

[woman] Oh no!

[Dallas] ...means she doesn't.

[woman, off-screen]
Get your horse please, Al.

[Dallas] Nah, I'll just get another one.

Maybe this one. Here we go.

Yes, and...

[woman yelps]

[Dallas] Oh. Never mind.

The water is deeper than expected

and creates significant hydrodynamic drag,

causing the horse to come
to an abrupt halt.

[woman yelps]

[Dallas] But she doesn't.

Ever get the feeling your horse
just doesn't really like you?

[electricity crackling]

[creaking, clattering]

Can you guess what science
these hotel hijinks

are about to demonstrate?

[glass shatters]

[electricity crackling]

[glass shatters]

[Dallas] Did you guess what science
he's about to show us?

[man laughs]

[Dallas] Yes, that's right.
It's moment of inertia.

This is an object's resistance
to rotational acceleration.

He throws his arms back
to generate angular momentum

but fails to tuck his arms and legs in

to reduce his moment of inertia,

so he doesn't rotate fast enough

to get all the way round before landing.

[man laughs]

[Dallas] I reckon he'll be in a single
room on their next trip.

[man] Oh, I'm not doing it anymore.

[Dallas] That's probably for the best.

[glass shatters]

[electricity crackling]

[glass shatters]

Whenever I go to the gym,
which is clearly very often,

I find myself spending most of my time

waiting for the equipment to become free.

Fortunately, some enterprising
fitness enthusiasts

have come up with a solution.

They forget the barbells

and simply squat-lift their friends.

Hey!

It's just too much fun.

And even if you can't do it...

[both scream]

[Dallas] ...well, hey, it's still fun!

[man] Come on. Lean.

[Dallas] Yeah, uh-oh.

[woman] My chin hurts.

[Dallas] Although it is quite dangerous.

But for those who do insist
on squat-lifting their friends,

and, alas, there are quite a few,

a little science may help
with damage limitation.

An individual has a center of mass.

When someone else balances
on their shoulders...

the two people have
a combined center of mass,

which is higher.

When squatting,
the combined center of mass

must remain over the base of support,

which, in this case, is his feet.

It's trickier if his friend
is sitting upright on his shoulders,

as the combined center of mass
is even higher.

If the center of mass moves
outside his base of support,

a turning effect will be produced

and over they go.

We at the Science of Stupid are nothing
if not thorough in our studies,

so we sent our fittest researchers

to test the science in practice

in a variety of environments.

After careful consideration,
I thought I'd send

these two researchers to the beach.

[woman yells]

[Dallas] And now I regret it.

As her friend tries
to stand on her shoulders,

their combined center of mass
suddenly increases in height,

so when the friend slips back,

it's impossible to avoid a turning effect.

[woman yells]

[Dallas] Right, who's next?

Not sure about the picnic table,
but this approach certainly keeps

the combined center of mass lower...

[man yells]

[groans]

[Dallas] ...if a bit far back.

As he climbs on his friend's back,

their combined center of mass
is too far behind

his base of support,

and a turning effect does the rest.

[man groans]

[Dallas] Yeah, I think
we can lose the picnic table

next time, lads.

Can our junior researchers nail this?

-[girl] Sarah!
-[girl] Ah!

[clattering]

[Dallas] No, and they've ruined
Christmas.

[girl] Ow!

[Dallas] The girl being carried
leans forward,

attempting to keep her center of mass
above her friend's,

but her friend loses her balance,
which creates a turning effect.

-[girl] Sarah!
-[girl] Ah!

[clattering]

[Dallas] Yeah, this activity
isn't such a great idea.

I mean, barbells may be pricy...

but they're cheaper to fix than friends.

[bell rings]

[liquid splatters, glass shatters]

[bubbling, hissing]

It is time to limber up your lobes,
stimulate your synapses,

and get ready for today's science lesson,

the part of the show where we place

one scientific principle
under the microscope,

but can you guess what it is
from the following clues?

This fabulous football player...

these profound ping-pong skills...

and this mistimed mishap.

If you said the Magnus effect,

give yourselves a pat on the back.

This is the generation of a force

on a spinning cylindrical
or spherical object

traveling through the air.

Here's some science
that's gonna make your head spin.

He strikes the ball off-center,

which causes it to spin.

The airflow on one side
of the ball is deflected

in the direction of the spin.

This produces a reaction force
on the ball...

that causes it to move
in a curved trajectory.

On a lighter ball, the force
from the Magnus effect

will have a greater influence

because it has less inertia to overcome.

Tennis would be tawdry,
and football would be forgettable

if not for the Magnus effect.

Okay, notebooks away.

It is time for your test.

Question one: how do you generate

the Magnus effect on a ball?

Let's see if Dad can give us the answer.

[woman, off-screen gasps]

[Dallas] Good save.

Dad kicks the ball off-center,

which deflects the airflow
on one side of the ball, making it curl...

-[woman, off-screen gasps]
-[boy crying]

[Dallas] ...resulting in a bump
for little Messi,

but a world of pain for Dad.

Question two: will a lighter object
be more or less affected

by the Magnus effect?

Now for a home run.

[man] Oh!

[Dallas] Nope, just a run home.

They're playing with a Wiffle ball,

which is much lighter than a baseball,

so the Magnus effect is more pronounced.

As the pitched ball spins,
it curves more in the air.

-He still nails it.
-[man] Oh! Oh, my God!

[Dallas] But, you know, sometimes,
it's just not your day.

Here is the last question, number three.

What happens when a ball has less spin?

Let's see.

It goes pretty much in a straight line.

He strikes the ball close to the center

so fails to generate the correct spin...

and curl it over the wall.

He nearly scored, though,
just not in the right goal.

Class dismissed.

[glass shatters]

[electricity crackling]

[Dallas] Tides are one of the most
reliable phenomena in the world.

Most of the time, they gently rise
and fall almost unnoticed,

but every now and then,
we are reminded that tides represent

over 70 percent of
the Earth's surface on the move.

To harness the raw power of the ocean,

some learn to exploit
its predictable ebb and flow.

Others completely ignore it.

[man] Ooh!

[man, off-screen] I told you!

I knew that was going to happen.

[Dallas] You and I both, sir,

but I'd keep that to yourself.

Tides, of course, are the rise and fall

of sea level
caused by the combined effects

of the gravitational forces
exerted by the Moon and the Sun

and the rotation of Earth.

And if all that sounds
a little bit complicated,

and it is, well, here's how it works.

The gravitational attraction from the Moon

acts more powerfully
on the side of the Earth

that faces it.

This pulls seawater towards the Moon,

causing a vast bulge in the ocean.

On the opposite side of the Earth

where the gravitational attraction
of the moon is weaker,

centrifugal force exceeds
the gravitational force,

and the water moves away from the Earth,

also forming a bulge.

Tidal range is the difference in height

between low and high tide.

If a beach is flatter,
the tide will travel further in and out

for the same tidal range.

So, you can now see why,
when you head to the beach,

it's crucial to check
the local tidal timetables.

Low tide is perfect for capturing
the romance of the sea.

[woman screams]

[Dallas] But this is high tide.

The moon's gravitational pull on the sea

meant the tide was high.

The waves crashed high over the rocks.

[woman screams]

[Dallas] And our mysterious mermaid
was returned to the sea.

[woman, off-screen coughs]

[Dallas] I can't see, is that high tide?

Yep, yes, it is.

And don't forget,

the tide will travel further
if the beach is flatter,

so this is not the best place
to leave your car.

Maybe try a car park.

Oh, and one last piece of bonus science.

It's not just seas that rise and fall

with the tides, some rivers do too.

[man, off-screen] Oh my God!

There goes the top of his boat.

[Dallas] Now, to be fair, he had no
option

apart from that big open drawbridge
just to the left.

[electricity crackling]

[clattering]

In baseball, it's often the batting

and the pitching
that gets all the attention,

but once you've sweetly struck that ball,

you still need to race from base to base

without the catcher tagging you.

That may sound simple,

but it requires
a surprising array of skills.

You need speed and agility...

perseverance...

[screaming and shouting]

[woman, off-screen] Whoo!

[woman, off-screen screaming]

[Dallas] ...and an appetite...

[laughter]

[Dallas] ...for dirt.

And you're also gonna need to get a handle
on some essential science.

In particular, momentum and friction.

Our man needs to build up momentum

from a standing position.

To avoid being tagged, he slides into base

using his momentum to carry him forward

and friction with the ground
to decelerate.

If he slides too early,

friction with the ground
will overcome his momentum

before he reaches the base.

Delino DeShields, one of the fastest
base runners in the game,

has an average top speed
of 30.5 feet per second.

That's only 10.3 feet per second slower

than Usain Bolt's hundred meters
world record speed.

Can this runner break that record?

No, that is slightly slower
than 30.5 feet per second.

He slides too early,
and the large coefficient of friction

brings him...

to a sudden halt.

[hushed] Don't worry, no one noticed!

[laughter]

If your velocity is a little lacking,

why not catch a lift from a grown-up?

[boy] Come on!

Whoo!

[Dallas] That's why not.

They had plenty of momentum,
but their combined center of mass

was too far forward
and went beyond their base,

and not the base they were aiming for.

That's it, fella, don't worry about her.

It's all about the winning.

And now, for one of our
younger sports stars, Hayley.

[man, off-screen] Come on, Hayley!

[woman, off-screen] You can do it!

-[girl screams]
-[Dallas chuckles] No, she can't.

Hayley builds up momentum beautifully,

but, well, she trips.

Luckily, the catcher drops the ball,
and a sliding Hayley overcomes friction

and makes it by a nose.

So nail momentum and overcome friction,

and you're safe.

[woman, off-screen] Oh!

[Dallas] But you do also need
to use your eyes.

[glass shatters]

[electricity crackling]

[glass shatters]

It is reported that the science-fiction
filmmaker David Cronenberg once said,

"Everybody's a mad scientist,
and life is their lab.

"We're all trying to experiment
to find a way to live,

to solve problems,
to fend off madness and chaos."

By the looks of things, this lot need
to experiment much more.

[woman screams]

[girl screams]

[laughter]

[man] Ah!

[woman screams]

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

[laughter]

[woman, off-screen gasps]

[man, off-screen laughs]