04x14 - Bridges, Snowboarding and Tug of w*r

[bunniefuu]

[Dallas] This is the Science of Stupid.

[reading]

Yes, this is the show
that combines serious science

with stupid stunts,

where we can enjoy a multitude of mistakes

and analyze what went wrong.

Through their pain, we'll gain an insight

into scientific principles
like centripetal force...

momentum...

and tensile strength...

or lack thereof.

Science is the master,

and we must respect its laws

or suffer the consequences.

So don't try any of this at home

-or even in your head.
-Ahh!

[Dallas] It's the Science of Stupid.

In this show,

we'll learn about parabolic trajectory...

torque...

and angular momentum.

[scream]

But first this.

When I first started wearing
leather trousers,

people thought I was having
a massive midlife crisis,

but they were wrong.

It was actually to stop this
from happening again.

[man] Right.

Ohh!

Oh!

[Dallas] You only make
that mistake once in life.

Yeah, with zip lines,
there are things you need

to watch out for, like your speed...

Oh!

[Dallas] Your landing zone...

Ugh!

[Dallas] And, of course,
exactly where you put the guide rope.

[laughter]

Going down a zip line is the easy bit.

You just hold on and hope for the best.

It's the getting off that requires
an understanding of science,

and that starts by knowing that energy

can't be created or destroyed,
only converted to other forms.

Our sliding man has
a lot of kinetic energy,

but this zip line has a stopper,
so he swings up like a pendulum,

trading his kinetic energy for
gravitational potential energy.

Another option is to gradually convert

his kinetic energy into heat
through friction,

or lose that kinetic energy more quickly

by generating a larger impact force.

So it's all about safely shedding

your kinetic energy.

Let's see if these guys
have been paying attention.

-Are you good?
-Uh-huh.

[Dallas] That soft tire should dissipate

his kinetic energy nice and gradually.

Argh!

[Dallas] That was a bit sudden.

And when his feet come off,

he experiences angular velocity,
then gravitational acceleration,

and then impact force.

Maybe these guy swill have better luck
trying to slide the right way up.

[man laughs]

[Dallas] Yep, that stopper
dissipated his kinetic energy,

but in doing so it converted
his linear velocity

into angular velocity,
turning him into a pendulum.

This guy sensibly has a foot strap

to help him stay in control...

[woman laughs]

[Dallas] Which it doesn't seem to do.

That foot strap spins him around
even faster...

[woman laughs]

[Dallas] And he now knows
what the forest floor tastes like...

piney with a hint of mushroom.

-[woman] Is it Tyler?
-[woman 2] Yeah, that's Tyler.

[Dallas] Tyler's gonna try his luck
using friction to slow down.

[woman] Oh, my God.

[Dallas] Well, he did stop,
so it sort of worked.

The fastest zip line in the world

hits over 100 miles an hour.

Tyler's not going that fast...

but it's fast enough.

[woman] Oh, my God!

[Dallas] Now, this lad has thought ahead

and has someone holding a rope

to gradually slow him down.

[woman] Oh, let go. Careful.

-Oh!
-Ohh!

[Dallas] And it probably works a treat.

To be honest, I was too busy watching
the rope lady get pulled in.

Oh!

Now, fairly obviously, I'm a bit of a star

on the basketball court,
a slam-dunk champ, if you will,

but I'm painfully aware
that not everyone has

my enviable physique and athletic prowess.

These are amazing basketball shots.

[Dallas] I think the viewers
will be the judge of that.

That wasn't.

Let's see how she does.

Oh, well, that's just cheating.

[woman screams]

[Dallas] It didn't seem
to help much either.

This kid wants his hoop sh**ting skills
caught on camera.

Let's hope it's worth it.

Definitely worth it.

To the many people
in the world who are not me,

the dunk might be out of the question,

but that doesn't mean
basketball can't be fun.

But what is the science behind
the skill of sh**ting hoops?

For maximum launch velocity,

he uses the kinetic chain
of his shoulder, elbow,

wrists, and fingers,
extending these joints in sequence.

The ideal launch angle
is about 50 degrees,

from as high as possible,

so it helps to be tall and to jump.

The launch velocity, angle, and height

determine the shape of the ball's curved
parabolic trajectory,

which if chosen carefully,

should coincide with the hoop.

Honestly, it is like watching myself.

And one last thing,
if you are on the move,

you need to watch your momentum too,

as that complicates things.

So that's the science,

but what about putting
all that theory into practice?

Oh!

[Dallas] Slam dunk.

When running towards the hoop,
watch your momentum

and where you're going.

Let's see how this kid manages
a classic layup.

Argh!

[Dallas] Well, he understands
about the kinetic chain,

but not apparently about perspective.

Argh!

[Dallas] With two basketball hoops
and a trampoline,

it looks like this kid
takes his b-ball seriously,

but that still hasn't improved his aim.

The world's longest basketball shot

is 112 feet, 6 inches.

Ohh!

[Dallas] All right, calm down.
That was 112 feet no inches.

[laughs]

When you finally have the hang of it,

you can try what people call
the no-look shot.

To the uninitiated,
that is sh**ting backwards

and overhead, and with a bit of practice,

you'll be getting baskets all day long.

All day.

-Argh!
-[Dallas] More practice needed.

Like this guy trying out a trick shot.

-Oh!
-[laughs]

[Dallas] I don't think
he's been paying attention

to the science at all.

A misjudged launch angle

means that when the parabolic trajectory
was interrupted by the wall,

it was also interrupted by the crossbar

and then his crotch.

That looks good.

Ooh, but in my experience,

it's always dangerous before
you know you've made your shot.

Ahh!

[Dallas] And that's what
you get for being smug.

Ahh!

It would be sick if I hit this.

[Dallas] It would.

Oh!

-[kid crying]
-[Dallas] Oh, dear.

This experimental chef
is going to tenderize his steak

using his wooden sword,

but what scientific principle is he about

to unwittingly demonstrate?

We asked you what science
this topless swordsmith

was about to show us.

-Hah!
-Oh, [bleep]!

[Dallas] Well, he's learned a little more
about class one levers.

When his wooden blade hits the steak,

it also strikes the table edge

and breaks from the underside.

As the rest of the sword
is moving downwards,

the broken end rotates backwards,

becoming a class one lever,
much like a catapult.

Oh, [bleep]!

[Dallas] Still,
I bet his meat's tender now.

I love skiing.

I mean, it's not really the skiing itself
that gets me going.

It's the freezing weather,
the overpriced hot chocolate,

and the near-death experiences
that I really get my kicks from.

[woman] What?

[Dallas] See what I mean? Spine chilling.

Ohh!

[Dallas] It has a huge attraction...

to those of us who love being in traction.

Now, this is impressive.

Look at him go... to a hospital.

Well, ski flips are hard

and best left to the professionals,

as I've learned to my detriment,

and that's partly because they're packed

with complicated science.

So why don't we take a look?

As he hits the ramp,
the more vertical velocity

our man achieves, the higher he'll go

and the more air time he'll have
to perform the flip.

For a front flip,
he needs to lean forwards

by flexing his hips as he launches.

This generates a forward lean
and angular velocity.

However, too much angular velocity

and he risks over-rotating.

And the reverse is true.

Too little angular velocity
and you can under-rotate.

Either way, he's in for
a bad time on landing.

So the perfect front flip
requires a combination

of fast enough takeoff velocity,

correct body position,
and controlled rotation,

and the same is true for the back flip.

It's just about explosively
straightening your knees and hips

to get that opposite rotation

and using the momentum
of your skis to help

carry you round. Simple.

Let's see how it should be done.

Whoa!

[man] Oh!

[Dallas] Well, not like that.

[man] Oh, my God!

[Dallas] He hits the ramp
with more than enough velocity,

generates too much angular momentum,

so he over-rotate sand loses his skis.

Oh, there they are.

Night jumping.

Now, this is a confident skier
hitting the ramp...

Oh, [bleep]!

And then hitting most of
the piste on the way down.

This time, it's too
little angular momentum

that's the problem, so he under-rotates,

and that's the point there where he wishes

he'd gone for the more
expensive travel insurance.

This guy is so confident
he doesn't even need poles.

Did he mean to do that? Is that a thing?

[all] ♪ Hallelujah ♪

[Dallas] After an amazing flip,

the hard landing stored
enough energy in his joints

to bounce him back onto his feet,

and off he heads,
presumably to buy a lottery ticket

before that luck runs out.

[bell rings]

OK, settle down at the back, please.

Jones, see me afterwards.
Thank you.

It's time for today's science lesson,

the part of the show where we drill down
into one specific scientific principle.

So who can tell me what the following
have got in common?

This acrobatic biker...

Ugh!

[Dallas] These teenage
playground enthusiasts...

-Ahh!
-[laughs]

[Dallas] And these guys...

who are clearly nuts.

Oh, my [bleep] back, dude!

If you said torque,
take five house points,

and in science terms, torque is
also known as a turning force,

which is the result of a force

moving a moment arm around a pivot.

A motorbike wheel
is designed to convert torque

from the engine into
linear force through traction,

propelling the motorbike forwards.

When our rider opens the throttle,

torque is applied to the back wheel.

Newton's Third Law tells us
that when one part

of a mechanism experiences
torque in one direction,

the rest of the object
experiences counter-torque

in the opposite direction.

So the body of the bike lifts
into the air.

When he applies the brake,
the opposite happens.

While the linear force of gravity
creates additional torque,

that helps to rotate the body of the bike
back onto the ground.

Torque is the result of a force
turning a pivot.

All clear? Let's see. Time for a pop quiz.

Question one, what happens when you use

a single moment arm to generate torque
at a wobbly pivot?

That's what I call a spinning class.

It's so important to rehydrate
after exercise,

so doing it in a bar is a smart idea...

[scream]

Eh, that's not so smart.

[groans]

[Dallas] This man is using a linear force

from his arm to apply torque
to his friend,

until her center of mass
strayed away from the pivot

and a wipeout was inevitable.

You're both barred.

[woman] Ahh!

Question two, can you identify a situation

where gravity can generate torque?

Oh, that.

This extreme off-roader
is using torque in the wheels

to propel him up a near-vertical cliff.

However, when the vehicle falls sideways,

it's less able to resist
the torque generated by gravity,

and he rolls down the cliff.

This BMX-er demonstrates torque

by converting the linear force
into angular momentum.

Ohh.

[Dallas] Close, but no cigar.

At least he took it on the chin.

Ohh.

All right, third and final question.

To convert between torque
and linear forces,

what else to do you need?

Exactly, a moment arm and some traction.

Useful stuff, torque.

Oh!

[Dallas] As long as you know
how to use it.

Class dismissed.

Oh!

I love exploring the world

and getting away for a bit of a break,

but when you're booking a holiday,

you really, really need
to read the small print

or you can get into big trouble.

This guy has totally
misunderstood waterskiing.

[man laughs]

[Dallas] This man thought sport fishing
would be relaxing.

-Whoa.
-Whoa!

[Dallas] And this iguana
had been led to believe

the lilos were a lot bigger.

You might have noticed that everyone
was trying to stay afloat,

and that's something
that many animals can do

much better than us.

So let's dive headfirst into
the science to find out why.

In water, any object
generates a buoyant force

that is equal to the weight
of the water they displace.

If this buoyant force
can balance their weight,

the animal will float.

A less dense animal
will float higher in the water,

thus reducing hydrodynamic drag,

which makes it easier to swim.

A more dense animal will sink deeper,

displacing more water to generate

a large enough buoyant force
to balance their weight.

And many water-going animals
with fur or feathers

have an oily hydrophobic coating.

This helps them avoid getting waterlogged,

which would increase
their overall density.

Staying afloat is all about buoyant force,

hydrodynamics, and hydrophobic materials,

but even for animals that like the water,

it's not always plain sailing.

Like this dog.

Looks like he's having a great time...

or at least he did.

[whines]

Dogs get easily waterlogged

and have a lower buoyancy
than water-dwelling animals,

which is easily overcome
by his friend bombing him.

[woman] You look terrified!

[Dallas] Terrified and dog tired.

Aww.

[whining]

This cat is a feline scientist
trying an experiment.

He wants to land on the ring
without falling in.

The thing is,
cats don't understand physics.

Without a hydrophobic coat, he gets wet,

becomes waterlogged, and then struggles

to get traction on
the low-friction sides of the bath.

Don't be embarrassed.

It's only by failing that we learn.

I've always found that nothing
livens up a party

like a little limbo.

A bit of flexibility can go a long way,

and the more laid-back you are,
the more successful you will be.

So let's see, how low can you go?

[woman laughs]

[Dallas] That was dreadful.
Maybe you need to warm up first...

like these ladies.

Well, I bet her face is warm now.

Ahh!

[Dallas] But when you're
stretched and ready,

you can try your limbo with speed.

-Maybe a bit less speed.
-[whines]

To properly explain why they
failed to beat the limbo,

we'll need to get our heads
around the science.

Our gymnast knows that the
secret to successful limbo

is modifying her body position
to get her center of mass

as low as possible

whilst keeping it above her base
of support.

To do this, she squats down

and pushes her legs out to the sides.

Using extreme knee valgus,
her knees collapse inwards

with her weight supported
on the inside of her feet.

She then leans her torso backwards

to lower her center of mass,

using flexibility and core muscle strength

to maintain the position.

To keep her center of mass above
her base of support,

she keeps her legs in position
so that her feet

stay beneath her
and moves forwards using small,

deliberate movements to maintain balance.

It sounds easy enough to become
a limbo legend,

and trust me, I know, but it isn't.

I have a feeling that we are
going to have to set

a very low bar.

Let's see if this rocker
has got what it takes.

Well, he made an attempt at a knee valgus,

and he made it under the bar,

but when he tries to take a step,

his center of mass moves forwards,

but his feet are still behind him,

and he topples.

Not much rock, quite a lot of roll.

Whoo!

[Dallas] This is nice to see,
an impromptu street limbo.

This guy looks like
he knows what he's doing.

[woman] Ahh!

[Dallas] Well, that's it.
That's game over.

He lacks the flexibility necessary
to bend his body back far enough,

and his center of mass
is too far forwards.

Yep, you're still gonna need
to pay for your parking, though.

Using a vehicle means you don't need
to shuffle under the bar.

Nice work, lads.

[engine revving]

[tires screeching]

[Dallas]
You do still need to steer, though.

[man] Mr. Motorcycle Man,
you are kicked out.

[Dallas] That is quite right,
awful limbo etiquette.

[tires screeching]

Charles Darwin once famously said

that ignorance more frequently
begets confidence

than does knowledge,

and as if to prove his point,

look at how confident this lot are.

[woman] What?

Oh!

Ahh! Ugh!

[woman] Ahh!

Ugh!

Ah!

Argh!

-Ahh!
-[laughs]

[laughs]