03x09 - Snowboards, Hoppers and Football

[bunniefuu]

[Richard]
This is the Science of Stupid.

Yes, this is the show

that shines an analytical spotlight

on the most foolish of the brave,

as they push the boundaries

of both science and stupidity

so we don't have to.

Without their mindless misadventure,

we couldn't demonstrate principles

such as pendulum effect,

trajectory,

and not forgetting that old classic,

velocity.

So sit back and tuck in to a massive slice

of the Science of Stupid.

[electricity crackling]

[Richard]
In this show, we'll get to grips

with the soggy side of drag.

We'll explore the ups and downs

of inertia

and how conservation of energy...

makes beds bouncy.

But first, this.

[glass shatters]

[electricity crackling]

[glass shatters]

[Richard]
When you think of drifting,

chances are you're thinking of this.

Cars taking corners at high speed,

losing rear wheel traction,

resulting in lots of smoke

and lots of sideways fun.

But not for everyone.

So, what if you don't have a car?

Surely you can't drift a motorbike.

It's time to wake up
and smell the burning rubber.

Oh, yeah, what doesn't look good in gold?

To drift turn on a bike,
you need three things:

a lot of rubber, a lot of throttle,

and a bag load of courage.

Here's the science.

To start a drift turn,

the rider blips the throttle
and then brakes sharply.

This will instigate the loss
of traction to the back wheel.

Due to its inertia,

the rear wheel will attempt
to continue in a straight line,

swinging the back of the bike out.

The front wheel still has traction,

allowing it to counter steer

in a circular path around the bend.

So it's a case of losing traction

from the rear wheel, balancing the bike,

and letting the front wheel
steer you round the corner.

What could possibly go wrong?

This couple are on their first date,

and she's made
the big mistake of asking him

what he does in his spare time.

And he's made the even bigger mistake
of showing her.

This rider couldn't keep
his speed high enough

to maintain the centrifugal force
on the bike,

so he leaned too far
and gravity took control.

[booming thud]

Now put your shirt back on.

You'll get a cold.

This lone dr*fter

doesn't have anyone to run circles round,

so he's learning to counterbalance
the rapid shifts in direction

just for fun.

Then now he isn't.

On loose surfaces,
drifting can be the fastest way

to get around a corner,

and there is a type of motor sport
that has turned it into an art form.

This is Speedway,

fast and furious racing on dirt tracks.

The riders drift to change direction
around the corners

without decelerating and losing thrust.

[man screams]

[Richard] Unless they do that.

With his front wheel off the ground,

he could no longer counter steer,
and he was out.

[man screams]

[Richard] Cheer up.

Remember,
it's the taking part that counts.

Drifting in close formation
makes for spectacular racing.

When one rider goes, they all do.

If you lose your drift in Speedway,

you lose the race.

The bike's rear wheel
briefly gained traction

and the sudden force unbalanced the rider.

Ah, what a way to go!

[electricity crackling]

[Richard] We scientists
are more used to testing

our intellectual strength
than our muscular might,

but when it comes
to lifting heavy objects,

it can pay to give your brains
a quick flex before your brawn

by considering a few safety pointers.

The higher you lift something,

the further it has to fall.

[woman screams]

[Richard] Oh! Butterfingers.

Ensure the object to be lifted is secure.

[laughter]

[Richard] And when lifting
awkward-shaped loads...

[man, off-screen]
Go ahead, Superman!

[Richard]
...it's best if a friend helps you

instead of filming you.

[man, off-screen]
You ******* kidding me?

[Richard] Believe it or not,

those guys were not actually
professional weightlifters,

but for those who are,
few disciplines demonstrate

the ability to lift heavy objects

quite like Olympic weightlifting.

This lady is attempting
a two-stage Olympic lift

called the clean and jerk.

First, the clean.

And now the jerk.

Oh, come back!

Who's gonna put that away?

The other Olympic lift
is known as the snatch

because you quickly lift
the weight above your head.

Hope he kept the receipt.

The record for a snatch lift
is over 470 pounds.

That's two giant pandas.

Now, we may be fresh out of pandas,

but we have got tons of science.

With a firm grasp of the bar,

he lifts with enough force

to give the bar
sufficient vertical momentum.

The swooping action can
create a turning effect

caused by the bar's inertia.

He counteracts this by bracing his body

to slow down the movement.

With his arms locked,

a final push from his legs

provides the power required to stand

using his skeleton's compressive strength
to support the weight.

Once you've nailed the technique,

getting a heavy weight
above your head is simple.

The tricky bit is keeping it there.

This muscle man is going
to perform a magic trick.

Now he sees it.

Now he doesn't.

-[man] You all right?
-[Richard] Bet he feels it, though.

The bar had way too much inertia

and he didn't apply enough force

to counterbalance it.

How're you feeling?

[man]
******* hurt.

[Richard] I thought so.

Ever wondered why weightlifters

often have people nearby
to spot their lifts?

It's to stop that.

Failing to lock his arms

meant he couldn't control
the inertia of the bar,

which was a right pain in the neck.

Let's face it,
with all of that inertia to deal with,

even super-strong athletes
are gonna overcook it occasionally.

So to avoid becoming
another heavy metal casualty,

you need to learn how
to drop the weight safely.

It's a question of knowing when to let go.

That was a bit late, mate.

Fighting a losing battle with inertia,

he should've dropped the bar
a lot earlier.

I'd stay down there, fella. Much safer.

Time for one last lift.

There you go. Textbook.

Bad luck. Seven years of it, to be exact.

[electricity crackling]

[Richard] Now, can you guess
what scientific principle

one of these piñata players
is about to demonstrate?

[glass shatters]

[electricity crackling]

[Richard] Did you guess the science
she's about to show us?

It's momentum and impact force.

As the end of the bat accelerates,

it gains lots of momentum

for enough impact force
to smash the sweets

out of the piñata,

or the nose on your friend

which is anything but sweet.

[electricity crackling]

[Richard] If you've got a problem,
science usually has the answer.

Take the alpine snowboarder

looking for something to do
in the hotter months.

Science says that snow turns
to water when things heat up.

And that's why we invented wakeboards.

Ah, can you have too much fun?

[woman screams]

[Richard] Ah, seems you can.

Okay. Before we don our wetsuits,

let's dip our toes into the science.

To stay balanced,
he keeps the tip of the board

above the surface

and leans his center of mass back,

counteracting the force
from tension in the cable.

By moving in an arc,

he uses centripetal force from the cable

to gain speed side to side.

Effectively covering more distance

over the same time.

Accelerating from nought
to 20 miles an hour

whilst being dragged through water

with planks of wood strapped to your feet

isn't actually as easy as it sounds.

This beginner's instructor
is reminding her

that she needs to lean back

to counteract the force
of a speeding towboat.

What was that you were saying, mate?

She was so busy learning the ropes,

she forgot all about the rapidly
accelerating speed boat at the other end.

Shouldn't that be attached to her feet?

Once up on the water, you could lean back

and enjoy the ride,

or you could bounce over the boat's wake

using centripetal force
to turbo-charge your speed.

Like this guy.

Swinging behind the boat
allows him to travel

nearly one and a half times
faster than his motorized tug.

Who needs a board anyway
when you've got a back?

Practice makes perfect,

and you'll soon be
harnessing centripetal force

to bunny hop the wake like a pro.

When you're really good,
you can even touch the water...

with your face.

And when the time has come
to call it a day,

why not use all of that centripetal force

to glide you back to shore?

Well, almost.

[bell rings]

[bubbling]

Comics and catapults away, class.

It's time for your science lesson.

Hold on tight, because today

you're learning a principle
that can send you into a spin.

Hands up, who can tell me
how back-flipping bathers...

are scientifically coupled

to balancing fence walkers...

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

[Richard] ...and acrobatic bull riders?

[bull bellows]

That's right, today we'll be looking
at moment of inertia,

or for those of you at the back,

how easy it is for something
to rotate around an axis.

What we need is an example.

Exercise books out, page 18,
break dancing.

Once spinning, his angular momentum
cannot be changed

without a large enough external force.

So to spin faster,
he brings his mass closer

to his axis of rotation,

decreasing his moment of inertia

for greater angular velocity.

Stretching out increases
his moment of inertia,

decreasing his angular velocity,
and he spins slower.

Right, that was the theory
behind moment of inertia,

and I hope you were paying attention

because it's time for a test.

Question one:
Moment of inertia directly relates

to which other scientific concept?

This bar swinger should give you a clue.

That's right, it's angular momentum.

Flying through the air,
his angular momentum

could not be changed.

It's his moment of inertia
that dictates how fast he spun...

onto his face.

Having angular momentum
is all well and good,

but it's what you do with it
that really matters.

So my second question is,
how do you reduce

your moment of inertia to rotate faster?

You tuck your limbs in tight,

bringing your mass closer
to the axis of rotation.

Flipping nice party, by the way.

Room for one more?

Oh, dear.

Jumping off the wall generated
some angular momentum,

but he didn't tuck his limbs in enough,

resulting in a big moment of inertia,

when it should've been a small one.

These bouncy techno-stilts
should provide ample angular momentum

but will he be able to create
a small enough moment of inertia

to complete a back flip?

No. No, he didn't.

My third and final question is this.

Why would a tight-rope walker
want a large moment of inertia?

I'm guessing this fella
doesn't want to rotate.

Spreading his arms out
creates a large moment of inertia,

making it harder for him to rotate,

allowing him to safely make it
right the way to the other--

Oh, dear.

So close.

And yet so painful.

[bleep]

And that, class, is your lesson
on the moment of inertia.

Spreading out your limbs increases it.

Tucking in your limbs...

reduces it.

-Class dismissed.
-[bleep]

[glass shatters]

[electricity crackling]

[Richard] We spend
a third of our life in bed,

which means choosing the right one
is a very important decision indeed.

So here's a few helpful tips.

A good bedstead should last a lifetime...

[woman]
My Grandma's bed.

[Richard]
...if you don't swing on it.

If space is at a premium,
you can opt for bunks.

And finally, don't choose
the first bed you see.

You've got to try a couple.

[woman laughing]

[Richard] Sweet dreams.

Clearly, mattresses aren't designed

to be trampolines,

but if you insist on bouncing on your bed,

you ought to check out
the science of the conservation of energy.

Most mattresses are filled
with coiled springs,

so when we jump on them,

we store elastic potential energy
by compressing them.

The potential energy
is converted into kinetic energy

when they spring back.

More potential energy stored

means more kinetic energy returned
and a bigger bounce.

Bed frames are weakest at the joints

where the side rail connects to the legs,

so bounce in the middle
and steer clear of the corners.

Nighty night.

Bed bouncing is simple.

The more energy you put into your jump,

the bigger bounce you get in return.

So you can either jump higher,

or perhaps you can try...

the double bounce.

[man 1, off-screen]
What did you hit?

[man 2] I dunno.

[Richard]
It was your knees.

[woman, off-screen]
Do it again!

[Richard] Bouncing on beds
by yourself is great.

But it's so much more fun
when there's two of you.

The kinetic energy in Dad's belly flop

was converted
into elastic potential energy

in the air-filled mattress.

This was converted back
into kinetic energy

when his son was catapulted up.

Thank heavens for closed windows, eh?

[laughter]

[Richard] With all the bouncing
that goes on

we've always needed strong beds.

A popular myth has it
that the saying, "sleep tight,"

comes from the 16th century

when mattresses used to be
suspended on tightened ropes.

These days, we use wooden slats.

Just like the ones that were stolen
from this chap's bed.

If bouncing is high up
on your list of bedtime activities,

and I know it is,

you'll want to try before you buy.

I'd pass on that one.

A drop flop where the frame meets the legs

was all it took to shear this bed frame.

Sometimes even the smallest bounce
is all it takes.

Well, don't just sit there. Panic!

[electricity crackling]

[Richard] You know,
a question I often get asked is,

"Richard, I'm finding I'm not laying siege
to as many castles as I used to,

so do I still need a catapult?"

To which I reply, "Don't be ridiculous.

"Of course you do.

[man groans]

As long as you're not on the wrong end."

[man groans]

[Richard] Now, whilst the Romans
may have launched rocks,

we seem to have migrated
to launching our friends,

or at least trying to cause
them significant discomfort.

And while science may not
be able to tell us why,

it can at least tell us how.

The basic components
of a catapult are a beam,

a pivot point,
and a force to launch the projectile.

The further the pivot is
from the projectile,

the more force is required to launch it.

And the faster it will be accelerated.

So, it's all about applying enough force

to hurl your projectile/friend
an appropriate distance.

Not enough force there. Try again.

[man screams]

[Richard] That did it!

[man] Oh ****! You all right?

[Richard] My guess is no.

The central pivot
and relatively small force,

combined with the bad body shape
of the jumper,

meant that he didn't have
enough angular velocity

to complete the flip.

But he knows that.

[man] Ouch!

[Richard] Exactly.

This is more like it.

Offset pivot, two men, greater height.

What could possibly go wrong?

[man] Three, two, one!

[Richard]
Apart from that.

Big force,

weak lever.

If you find yourself without a catapult,

and it does happen,

sometimes the least likely of objects
can become a high-powered human hurler.

Like a basketball hoop.

The force is provided by pushing.

Not enough to launch him over the house

but plenty enough to launch him...

into it.

A playground seesaw
is just a harmless children's plaything,

but add some really big kids...

and you've got yourself
a flipping catapult.

The central pivot meant this catapult

didn't generate any extra speed,

but it was enough.

Best let the little ones have a go, eh?

So where's the catapult here?

Oh, there it is!

You see, all sorts of things
can be catapults.

Good amount of force,
good pivot point position.

And something to tell the wife about

when you arrive home with less teeth.

[glass shatters]

[electricity crackling]

[Richard] And that brings our misguided
mix of science and stupidity to an end,

but I'm sure we'll be back very soon

because, as Einstein once said,

"Only two things are infinite,

the universe and human stupidity."

And he wasn't certain about the first one.
Goodbye.

[lively fiddle music]

[woman screams]

[man screams]

[woman screams]