04x08 - Rocks, Wheelies and Face Planting

[bunniefuu]

[Dallas]
This is the Science of Stupid.

[reading onscreen text]

[military drumming]

Yes, this is the show
where we put the fun

into the fundamentals of physics.

Prepare yourself to see
foolhardy field researchers

do foolish things without
fully thinking them through.

We'll dissect what went wrong and why

with the help of such
scientific principles as...

brittle failure...

off-center impulse...

and the angle of attack.

In the battle between fools and physics,
there can only be one winner.

So don't try any of this at home.

Actually, don't try it at all.

Watch out!

It's the Science of Stupid.

[electricity crackling]

In this show, we'll be looking at...

-[screaming]
-angular momentum...

-No!
-tensile strength...

and the disadvantages of a bipedal gait.

-Oh!
-But first, this.

[electricity crackling]

I love horse riding.

Done right, it's the perfect example
of man and animal working in harmony.

Done wrong, and it's one of the most
dangerous pursuits on the planet,

right up there with naked bee-keeping.

Ignore the science,
and it's also extremely painful.

[cheerful music]

-[screams]
-Yep. That hurt.

-[screams]
-As did that.

Maybe no fences equal no pain.

[screams]

No chance.

Despite horses being domesticated
over 4,000 years ago,

staying on the back of one
is clearly not that easy.

But don't worry,

we at the Science of Stupid
are here to help.

As they gain speed,
the horse and rider build momentum,

which, as any schoolboy knows,
cannot be created or destroyed,

only transferred.

So when the horse stops,

the rider must position himself
and remain balanced

so his momentum is reduced
at the same time,

and he avoids becoming separated.

He does this using strong
abductor muscles

to squeeze his thighs
and clamp onto the horse

and strong core stability
to stay upright

against the forces
from the horse's movements.

So basically, hang on for your life,

don't let go,
and hope that the horse goes easy on you,

which is why I've always got
a few sugar cubes in my pocket.

Got it?

[horse neighs]

I don't think she's got it quite yet.

Her body position was all wrong,
so when her horse puts on the brakes,

she continues moving forward...

face first into that fence.

Nice approach.

Good jump...

Stop!

...terrible dismount.

With no saddle, this rider has
less friction with the horse,

so the odds of separation increase
when she tells him to stop...

Stop!

...and he listens.

Ah, what a sweet moment.

This eager young chap
is asking his cowgirl to the prom.

[horse neighs]

-[groans]
-Don't think the horse approves, though.

As he accelerates away at an angle,

his momentum rapidly increases,
while the rider is left behind...

-[groans]
-on her behind.

So there are some of the basics
of staying on a horse.

But you might also want to
avoid getting bucked.

When a horse bucks,
it transfers momentum to the rider...

like that.

And the law of conservation of momentum
means that when the horse bucks...

she is catapulted skywards,

before coming back to earth with a bump.

-[groans]
-[thuds]

Well, this weird-looking horse
should be a lot easier to stay on.

[girl laughing]

Oh, dear.

Even a little donkey can generate
a lot of momentum when it wants to,

so don't be stupid--

get a grip before you smash a hip,

as my granny used to say.

[electricity crackling]

Anyone, and I mean anyone,

who's seen me
on the dance floor will tell you

it is an unforgettable experience.

The Funky Chicken,
the Robot, the Lawnmower--

there ain't no dance move
I can't pull off.

I love how you can
just boogie on down anywhere.

[hip-hop music]

Like when enjoying the ball game...

[man] Ooh!

On the daily commute to the office...

Check out this guy's rear bumper.

Or in getting ready for school

whilst being secretly filmed
by your big sister.

Alicia, get out!

Twerking-- now, that is a dance
I can get behind.

Anyway, let's find out
the science behind the moves.

To properly twerk,

our man needs to make a succession
of backwards and frontwards pelvic tilts.

The main muscle groups used
include the rectus abdominis,

hip flexors, and the glutes.

Used together,
they create a force couple,

rotating the pelvis sinusoidally
with the oscillation timed perfectly.

So the soft tissues can be resonated,
hopefully in time with the music.

Then, make sure your center of mass
remains above your base of support.

Generating large forces
as you push back and forth

can overcome static friction,

or the material strength
of your platform,

making you tumble like
a dance floor novice.

So just remember the simple rules--

pulse, thrust, then rotate,

and I think you've got the hang of it.

This lad demonstrates
the power of interpretive twerking

to tell his mum they're out of milk.

Shame. He wasn't
tilting his pelvis enough.

And his mum
takes her twerking seriously.

It's amazing when
you finally find the one.

[woman] Aah!

Maybe he's just not that into you.

A weak force couple
and ineffectual sinusoidal oscillation

was this lady's undoing.

Along with a lack of common sense.

Yeah, this isn't going
quite to plan, is it?

Remember, keep a handle
on your pelvic tilt

and watch your weight
as you twerk up and down

on those inanimate objects,

as our field researcher, Big Dave,
is about to show us.

Well, Dave,
you've well and truly smashed that.

Feeble pelvic tilt,

mixed with the force
from Big Dave's weight, overwhelmed...

his mum's coffee table.

Expert kitchen fitters hard at work.

[screams]

That's gonna cost ya.

More squatting than tilting,
and a force large enough

to overcome the material
strength of their support

meant this renovation
went a little over budget.

Two twerking chums here

enjoying a little friendly rivalry
on the dance floor.

[screams]

Yes, nice move. Bonus points for that.

[electricity crackling]

-[singing operatically]
-What scientific principle

is this ice skating
Pavarotti about to show us?

[electricity crackling]

[man singing "O Canada"]

[Dallas] We asked you what physics
this patriotic anthem belter

was about to demonstrate.

[singing]

-[all] Oh!
-[Dallas] Exactly. It's friction.

Ice has a low frictional resistance.

Carpets, not so much.

When his skates hit the carpet,

the coefficient of friction
suddenly increases

and he experiences a large,
slowing force at his feet.

Which, combined with his inertia...

to create a turning effect.

And the reason for Canadians
to be proud.

-[man continues singing]
-[Dallas] O Canada.

[electricity crackling]

[engine revving]

Slightly embarrassing confession here,

but I got myself locked
in the office bathroom the other evening.

Luckily, there was still

a couple of researchers
around to help me out.

The white rhino!

[onlooker]
The white rhino charges!

The white rhino charging...
[shouting indistinctly]

[groans]

-[laughing]
-[Dallas] Uh, guys, I'm still in here.

And why are you in your underwear?

I was stuck for hours,

but it was lovely to see
our field researchers

taking inspiration from nature,

and that's not a bad idea
when it comes to acceleration,

as some other members
of the animal kingdom

leave us in their dust.

And science tells us why.

[dynamic music]

The undisputed king of the sprint
is the cheetah.

Their strong leg muscles combined
with a proportionally low body mass

produce a very high
power-to-weight ratio

to get them moving.

The running gait is also key
when it comes to final speed.

Whereas we are limited by
the practical extension of our two legs,

sprinting animals like
greyhounds and cheetahs

employ a form of gallop
in which they bend their bodies

while extending their limbs
at the same time

to increase their stride length.

So expl*sive acceleration
is mainly down to

high power-to-weight ratio,

and a faster running gait
also helps to achieve those top speeds.

Four-legged creatures, or quadrupeds,
have an obvious advantage over us bipeds.

Whoo!

Oh!

[Dallas] See what I mean?

Gangnam style!

That is not the proper dance.

-[dog growls]
-[laughter]

This dog is
a classically trained choreographer,

so it's no wonder he's upset.

Rex here only takes one step
to extend all four limbs off the ground,

but that was all it took.

Learn the proper moves next time.

Now, remember, it's not just about
having a nice long stride.

It's also about how heavy you are,

and therefore,
how hard it is to get going.

And despite their large mass,

elephants can run
at up to 15 miles an hour,

which is even faster than me.

[woman] No! No!

-[Dallas] Yes, I'm afraid so.
-No, no, no, no!

But don't worry,
that big body mass means

it could take a while
to get up to speed.

Faster! Faster!

-I think it's up to speed now.
-No!

Yeah, I'd put my foot down
if I were you.

Have you seen "Jurassic Park"?

[bell rings]

[objects clattering]

Quiet down, everyone, please.

Jones, that means you.

It's your own time you're wasting.

Yes, it's the part of the show

where we take the scalpel
of scientific exploration

to one specific principle and dissect it.

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

[engines revving]

This easy rider...

-Oh!
-[wheels screeching]

skid marks...

this glamorous granny...

Ah! Succe--

[screams]

[Dallas] Bottoms up.

...and this party animal.

Down in one.

They're all examples of stable
and unstable equilibriums.

But what does that mean, exactly?

As usual, science has the answer.

The stability of an object

is determined by the size and shape
of its base of support

and the relative position
of its center of mass.

A human pyramid
has a wide base of support

and a center of mass
roughly in the middle.

It is in stable equilibrium.

But as our acrobat is thrown
up onto shoulders,

the tower has a small base of support
and is in unstable equilibrium.

They need to make continuous corrections

to resist perturbing forces
and stay balanced.

OK, paying attention were we?

Well, let's find out. Question one.

Are humans inherently stable or unstable
when standing up?

-[applause]
-[overlapping chatter]

Well, this group are testing
the theory by showing us

what you can do if you can't
get hold of a ticket for the big game.

Clearly, they're unstable,
because humans inherently are.

When stacked on top of one another,

the tower they form
is even more unstable,

and it takes only a small
perturbing force to topple them.

[energetic music]

Hard to believe, but this teenager

has been carefully building
a pyramid of dominoes for over 16 hours.

-Aah!
-Which now seems like

a massive waste of time.

This structure is stable,
thanks to its large base of support.

But any perturbing force
applied to an individual domino

can instantly cause a chain reaction.

Ever thought about getting out?

Maybe meeting some girls?

Question two.

Can a stable object become unstable?

We asked three renowned professors
to test this principle.

And the results are in.

Our learned friends were able to prove
that the stability of the object

could be compromised
as their combined weight

exceeded the material strength
of the object itself.

Still, a good night was had by all.

Moving on. Question three:

can an unstable object
stay balanced on its own?

Why don't we ask this guy?

Ah, the answer's no, then.

An unstable object
needs continuous small corrections

to stay balanced.

And when he lands from the jump,
his feet aren't on the pedals,

so he can't apply
the necessary corrections...

and the outcome was inevitable.

But a fall doesn't have to be
balance related.

[groans]

Often, it's just down to
good old-fashioned stupidity.

Jumping from that height,

the guy hit with
more than five times his body weight...

so it's no wonder he's a little sore.

All right, class dismissed.

[electricity crackling]

If your life is anything like mine,
then you're forever being asked

what your favorite bit
of playground equipment is.

Mine's anything except the slide.

Ever since I was a child,
their slidiness has scared me silly.

To me, it seems like
they're up to something.

[mellow doo-wop music]

[music winds down]

[Dallas] Do you see what I mean?

[doo-wop continues]

Aah!

That looked deliberate.

Even as an adult,
I still have issues with them.

Aah!

After years of expensive therapy,
I'm almost OK with normal slides.

But those bumpy ones
give me the heebie-jeebies.

Luckily, science is here to help out.

As we all know, the steeper the slide,
the lower the friction,

and the more momentum
our man will build up.

But add bumps, and it all becomes
a bit more complicated.

His weight generates a reaction force
from the slide,

perpendicular to the angle of the slope.

As the slope angle changes,

the direction
of the reaction force changes...

redirecting his momentum.

And if he has enough momentum,

our man will launch from the slide
when the slope drops again,

and he'll get a bump on his bottom.

So there we go--
safely navigating a bumpy slide

is all about allowing
for that reaction force

and finding the right balance
of momentum and friction.

[playful music]

Ooh, this looks good.

[groaning]

Ah, but the increased
vertical component

of the last bump's reaction force

is going to make sitting down
unpleasant for a while.

[parade music]

Good idea.
A little water to cut down on friction.

But when he hits the bump,

his momentum is redirected,
and he launches off...

even gaining some angular momentum
for an unhelpful rotation.

Maybe this boogie-boarder
will have better luck.

-[laughter]
-Or not.

Using water as a lubricant
cuts down on friction,

so he builds considerable momentum,

which is redirected upwards
when he hits the bump.

So, just remember the science,

and you shouldn't have any problems
with bumpy slides again.

Yeah, I'm gonna stick to the swings.

-[thud]
-[groans]

[electricity crackling]

Now then, the humble vine,

used for millennia by man and monkey alike
to get from A to B.

It's also a great way
to show off to your mates,

but only if you get it right.

[rock music]

-[laughing]
-Which he hasn't.

Perhaps taking a massive run-up
will help.

Perhaps not.

If you're feeling too lazy
to walk around the pool,

why not use some overhanging vegetation?

Ah, yeah, that's why.

It's one of those universal truths--

to achieve a successful vine swing,
you need to understand the science.

Vines like this rope are flexible
and ideal for swinging.

As our acrobat starts to swing,
she exploits pendulum motion,

trading her gravitational
potential energy

for kinetic energy.

After the apex of the swing,

that kinetic energy then transfers back
to gravitational potential energy.

It's at the bottom of the swing

that centrifugal force and gravity
combine

to exert the greatest tensile strength
on the vine.

If it were to snap,
this is where it's most likely to do so.

Well, that's the theory,
buy let's see how it works in practice.

Hmm. He looks confident.

But I'm not sure that's enough
to hold your weight.

Yes.

Willow is strong and supple,

but there's only just enough
tensile strength

in two branches to support him,

and, combined with centrifugal force...

it becomes a bit too much.

The ideal plant for swinging off
is a liana.

It contains very little lignin,

the substance that gives woody plants
their rigidity.

So it's flexible enough
to bend as it swings

without compromising
on tensile strength.

[groans]

But that is a palm tree.

You can see why it's never
Tarzan's first choice.

It just doesn't have the strength.

Still, nice landing.

This mother and son team
are doing experiments

into how gravitational potential energy
is converted into kinetic energy.

Lovely stuff.

Let's see how Mum does.

-Aah!
-Mum's a bit bigger--

she won't like me saying that--

and the increased weight applied
more tensile stress on the branch,

making it more likely to break.

[screams]

And it does.

This guy knows that, for once,
science is on his side.

The tensile strength of this vine

is able to withstand
the weight of our adventurous swinger.

But, sadly, the seat
and the tree branch aren't.

And that was the last time
any of us saw him.

[electricity crackling]

Albert Einstein allegedly said

the difference between
stupidity and genius

is that genius has limits.

It's almost as if he watched
the Science of Stupid.

[lively fiddle music]

Stop!

Aah!

[growling]

Aah!

The white rhino charging...
[shouting indistinctly]

[groaning]

Aah!