03x17 - sh**ting, Body Slam and Loading

[bunniefuu]

[Richard]
This is the Science of Stupid.

-[electricity crackles]
-[glass shatters]

[alarm blares]

Yes,

this is the show where science
collides with stupid.

Watch in awe as ordinary people
take extraordinary risks

for amateur stunts and cheap thrills.

We'll explain what went wrong and why

with the help of
key scientific principles.

Such as kinetic energy...

[groans]

Newton's laws of motion,

and ground reaction force.

So sit back and prepare to be educated,

because this is the Science of Stupid.

[glass shatters]

[electricity crackling]

In this show, we'll be exploring
angular momentum,

chemical changes...

[students gasp]

...and impact force.

But first, this.

[glass shatters]

[electricity crackling]

[glass shatters]

As anyone who's had
a skiing holiday will tell you,

chucking yourself down a mountain

on two planks of wood
isn't without a certain risk,

but that's just half the story

because before you can ski
down a mountain,

you have to get up it,

with all the joys that a ski lift entails.

[man groaning]

Not sure that's how
you're supposed to use them.

[yells]

Or that.

At least this lot have made it to the top.

[all groan]

But any celebrations may be
a little premature.

Clearly, there are a few things
we need to sort out

on the old ski lift front,

so it's ski goggles off
and science goggles on.

Two common types of lifts
are chairlifts and drag lifts.

With a drag lift,
he must position his body

to absorb the initial acceleration
from the pole

before it drags him uphill.

With a chairlift, he should
also take care when dismounting.

He must apply a small extra force
to move away from it,

but if he doesn't have enough speed,

or there's suddenly too much friction
from the snow,

he won't escape the chair,

and its continuing momentum
could create a turning effect

around his feet.

Essentially, it's that drag lifts can be
a little tricky getting on,

and chairlifts can be
a little tricky getting off.

It's all tricky.
But let's start with drag lifts.

[man, off-screen] Go on, Dave.

[Richard] I hope Dave remembers
to use his mass

to counteract the force of the lift.

No. That's just falling over.

[laughter]

And so is that.

[man] It's so hard, to be fair.

[Richard] But not as hard
as Dave's making it look.

[laughter]

There's a reason they're called
"drag lifts."

[woman, off-screen] Let go!

[Richard] With his center of mass
too far forward,

he's unable to properly absorb
the lift's acceleration.

[woman laughs]

But the low friction of the snow
means the lift can still pull him.

[woman, off-screen] Dave, let go!

[Richard] Oh, great, it's another Dave.

[woman, off-screen] Let go!

[Richard] Best listen to your mum, Dave.

Uh, Dave? Dave?

Has he got earmuffs on?

Let go. Oh! Good lad.

Oh, it's big Dave.

You still not gone up yet?

[laughter]

I'd give up on that, mate.

Perhaps buy a sledge.

Shall we move on to chairlifts?

That's lovely.

Good momentum from the chair

plus a gentle push for extra force.

You see, it's really not that difficult
if you're concentrating...

[laughter]

...which they clearly weren't.

Not enough momentum to exit the chair,

safety bar pulled down
whilst getting off chair,

over-rotation in front of chair.

Apart from that, it was textbook.

Of course, there are other ways
of getting off the lift...

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

[Richard] ...but I wouldn't recommend
them.

[man, off-screen] Wow.

[electricity crackling]

[clatters]

[Richard] Making an impressive entrance

is all dependent upon being able to master

that most basic of technologies: the door.

I'm sorry to say, it appears that
not everyone has mastered it,

so here are three golden rules to...

opening a door.

Always know where the door is.

There it is.

Always anticipate when a door...

is going to open.

And never try and break down a door...

that's already open.

Obviously, breaking down a door
is a terrible idea,

but I think we have to accept
that we are dealing with people

who seem incapable
of using one of these,

or, indeed, one of these.

So, for the terminally daft,

here's the science
behind breaking down doors.

Newton's first law tells us

that every object with mass has inertia.

The more mass the door has,

the larger the inertia
that will have to be overcome.

The force exerted on a door
will depend on the acceleration

of the mass that hits it.

Force is most efficiently used
by applying it

in the direction the door opens
and as far away

from the opening axis, the hinges,

as possible
to maximize the turning effect.

So, to break down a door,
you need enough force

and to use it quickly
and in the right place.

Clearly, this is something
only to be done in an emergency

and preferably by
serious emergency service professionals.

Here we have
a child-hammer combination.

[boy, off-screen] Do it.

[Richard] His force is too concentrated,

so he's just damaging
rather than opening the door.

Mummy will be pleased
when she gets home.

What's he going to use
to break open his door?

-[groans sharply]
-Oh.

Not enough force,
and not the ideal impact area of the door.

Or of his body, come to that.

[man groans]

Right, who's next?

Oh, it's them.

By using extra mass
and enough acceleration,

these enterprising fellows

have managed to break down a kitchen door

with a perfectly good handle.

They must be hungry.

Ah, the blushing bride,

or, in scientific terms, extra mass.

How romantic.

Great acceleration, plenty of mass,

but poor sense of direction,
and door already open.

If you were planning to carry
her over the threshold, mate,

it's a little to the left.

[electricity crackling]

[creaking]

[clatters]

Can you guess what scientific principle

these playground swings
will be used to demonstrate?

[glass shatters]

[electricity crackling]

[glass shatters]

So, have you guessed the science
we're about to see?

[laughter]

Yes, it's turning effect.

By letting go, when his center of mass
is behind his base of support,

the opposing forces of his mass
and the swing seat

resulted in a turning effect
that rotated him...

to his face.

[electricity crackles]

[clatters]

If you had to pick a thrilling water sport

to really get the old pulse racing,
what would it be?

Maybe jet skiing.

Yeah!

Or possibly surfing.

Cool!

Hold on a minute,
what about that new craze

everyone's talking about?

You know, what's it called?

Paddleboarding.

A bit like surfing

but with all the excitement
of a floating plank.

And if you're wondering
what could be more uncool

than riding a paddleboard...

[woman yells]

How about falling off one?

Yep, being bad at something

that a kitchen cupboard
could probably do if it had hands

has to be avoided at all costs.

So, without any further ado,

I suggest you direct your gaze
towards the science.

On a paddle board,
he wants to remain upright

with his center of mass
above his base of support.

The higher the center of mass,

the greater the turning effect
if the board tilts.

He can help his stability
by distributing his mass

over a larger area.

This increases the moment of inertia,

which makes it harder to rotate
but not impossible.

If you do manage not to fall off,

you can go quite a distance
on these things.

In fact, in 2007,
a chap called Wyatt Werneth

paddled 345 miles up the coast of Florida.

Must have been a slow afternoon.

So let's see if there's any way

we can make paddleboarding
remotely interesting.

This lady is combining her trip
with a little bodybuilding display.

[woman] Have you had enough flexing?

[man, off-screen] Never too much flexing.

[Richard] I think I have.

Can we have some paddling?

[man, off-screen]
Oh, you're gonna biff it.

Oh, you're gonna biff it!

[both laugh]

[Richard] That isn't the sort
of paddling I meant.

[man, off-screen] Yeah.

[Richard] Yes, because she moves
her center of mass

outside of her base of support,

the board gives way under her.

[man, off-screen] Lisa.

[man] Go practice some more.

[Richard] Good idea.

Remember that spreading your mass out
will increase your stability.

Yeah, not quite what I had in mind,

[woman screams]

And that's why.

Some people try to inject excitement

by pretending they're in a horror film.

[screams]

Yeah, absolutely terrifying.

A slight bump causes the board
to stop suddenly,

but her upper body continues,

upsetting her balance...

and hers.

Other things that can affect
your balance includes waves,

wind, weight distribution--

-[clicking]
-Oh!

And dolphins.

See?

[bell rings]

[beaker shatters]

[gurgling]

Right, settle down, you lot,

and if anyone at the back
can't see the blackboard,

don't worry, there isn't one.

But what we do have is
a very important science lesson.

If you want to know the theme
of today's lesson,

you're going to have to tell me
the difference

between the following two things...

[indistinct chatter]

A man you should never invite
to a children's party...

[man] ...two, one.

-[children screaming]
-[laughter]

[Richard] And someone who's now
regretting licking a frozen pole.

[unintelligible]

What was that?

No? Well, the first involved
a chemical change,

and the second a physical change.

And our lesson today is about
the difference between the two.

In a physical change,
molecules are rearranged

as a substance changes state.

In a chemical change,
new molecules are formed,

creating new substances.

With both, energy,
often in the form of heat,

is used up or released.

Yep, it's complicated.

So how about a couple of examples?

As popcorn kernels are heated,

water molecules inside are rearranged

as they turn to steam...

expanding outwards until the kernel pops.

So this is an example
of a physical change.

When sodium iodine is added
to hydrogen peroxide,

the hydrogen peroxide molecules
break apart...

Forming new substances,
including oxygen,

which is mixing with
some added dish soap

to create the foam.

It's a chemical change.

And now a little test to see
if you were paying attention.

Question one: what often gets released

or used up during a chemical
or physical change?

It's heat energy.

[man, off-screen] What the ****!

[Richard] Some liquid in the mold
was instantly changed into a gas

by the molten aluminum
and expanded underneath it.

[man, off-screen]
What the **** just happened?

[Richard] Liquid into gas,
a physical change.

[man, off-screen] Keep blowing.

[Richard] It'll be quite hot.

-[man 1] Yeah.
-[man 2, off-screen] Right there.

[Richard] Is that a potato g*n?

[man] Oh ****!

-[Richard] Yes, it is.
-[groans]

Gas combusts in tube,

creating heat in a chemical change.

Potato accelerates into him,

creating something a bit more physical.

Question two, what happens
in a chemical change?

[Professor] Are you ready?

[student, off screen]
I'm terrified. I'm terrified.

[Richard] Don't worry,
you'll be quite safe.

[students gasp]

Well, safe-ish.

And to answer the question,

it's that a new chemical substance
is formed.

The burning methane gas
reacts with the oxygen in the air

to form carbon dioxide and water.

Sir's lessons were great fun,
providing you sat at the back.

Question three,
what happens to the molecules

in a physical change?

[indistinct chatter]

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

[Richard] They get rearranged.

In this case, the carbon dioxide
molecules spread out,

and the bubbles rapidly expand.

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

[Richard] Can someone find a cloth...

and possibly his thumb?

[laughter]

When the liquid leaves
these extinguishers,

it'll become a gas

as the molecules become rearranged.

This is gonna be brilliant.

It's gonna work.

-[man] Oh, I think I broke it.
-[Richard] No.

It's not very good for a jet pack,

but at least he's not on fire.

So that concludes our lesson
on chemical and physical changes.

[man] I can't feel my arm.

[Richard] Yeah, that's physical.

[glass shatters]

[electricity crackling]

Nothing screams complete
and utter disaster

quite as loud as the sound of
a grown man trying to ride down

a hill on a BMX bike.

Especially a small one.

Or over a ramp.

[screams]

Nice glove, but next time, wear a helmet.

[indistinct yelling]

I can tell what you're thinking.

If they just stuck
to riding on flat ground,

things would be a whole lot safer.

Like these guys doing something
called flat landing.

And, no, it's not a whole lot safer.

Flat landing is the art of doing
BMX tricks on a flat surface,

the majority of which involve

much the same scientific principles.

So to get you started
on the road to downtown flatland,

here's the science behind a classic trick
called the Time Machine.

Traveling in an arc
with his feet on the rear pegs,

he shifts his center of mass slightly back
to get into a wheelie.

Moving a foot from the peg
and a hand from the handle,

he then brings his mass
towards the axis of his spin,

reducing his moment of inertia.

Due to conservation
of angular momentum,

this means he'll spin faster.

It's all about balance
and controlling that momentum.

Get that right, and you're halfway there.

Let's start with the basics
and getting the wheelie part sorted.

This chap is doing a front wheelie.

Nice use of center of mass.

Looks like he's got everything
under control.

-[indistinct chatter]
-[bowling pins rattle]

Ah!

Oh, another wheelie.

[man, off-screen]
Did you catch your ba*ls?

[Richard]
Yeah, it's a BMX thing, apparently.

By holding the wheel as he dropped,

it rotated away from him,

meaning when contact was resumed,

it wasn't with his feet.

That's the wheelie part,
but what about the spinning?

This is more like it.

-[man yells]
-And that wasn't.

To stay balanced, he relies on friction
between his feet and the bike,

but he didn't have enough friction

except on his face at the end there.

Is this guy doing a Time Machine?

Yeah... Oh, no, well, almost.

It would have been if he'd kept
his center of mass closer

to his spin axis, but he didn't.

Nice hat.

Is that a good idea?

-[man] Ow!
-[Richard] Apparently not.

The bike doesn't rotate
a full 360 degrees,

which he can't see.

He falls off, which we can see.

[electricity crackling]

[creaks]

Back in 1957, in a New Jersey garage,

two inventors came up
with what they thought

would be a revolutionary new wallpaper.

It wasn't. It was bubble wrap.

Hardly ideal for decorating your kitchen.

And not a lot better for fashion.

Oh, anyone got a dustpan and brush?

Yes, the attributes of bubble wrap

that keep those fragile things safe
when you pack them

can also offer protection

if you have a sudden urge
to start a new contact sport.

And here's the science that explains why.

The compressibility of air in bubble wrap

reduces the impact force

by increasing the duration of an impact.

The tiny space between the bubbles

means that even small objects
are likely to come into contact

with more than one bubble,

which increases the size
of the impact area,

decreasing the pressure.

It also helps conserve the kinetic energy

from a collision and converts it back

into kinetic energy
in the opposite direction.

So really what you have
are hundreds of tiny springs,

which will absorb a force
and then push back again.

It's meant to keep stuff safe.

Let's see if it works.

These guys have got
lots of bubble wrap...

[laughter]

Which, upon impact,
absorbs the kinetic energy

and then transfers it
in the opposite direction.

Yeah! Great bouncy fun.

Now get back to work.

One property of bubble wrap
we haven't mentioned yet,

and arguably the most important,

is the ability to do this.

[bubble wrap popping]

Is there anything more satisfying?

Cats like bubble wrap too.

With their small mass,

they're having to use their sharp claws

to minimize the surface area
over which the force is applied.

But, with bigger feet,

humans need more force
to pop the bubbles.

So falling over really helped. Nice one.

[glass shatters]

[electricity crackling]

[glass shatters]

And there you have it.

Plenty of reasons why
you should be more scientific

and less stupid when you ski,
cycle, cook, paddle,

wrap a parcel, or forcibly open a door.

So until the next time,

perhaps safer to stick to
some quiet reading

and no sudden page turns.

Goodbye.

[screams]

[screams]

[yells]

[students gasp]

[woman screams]

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

[laughter]