08x09 - Kayak Surfing, Biking and Felling Trees

[bunniefuu]

DALLAS (off-screen): This

is the Science of Stupid.

DALLAS (off-screen): Yes,

this is the show that splices scientific reason with

the DNA of stupidity.

Witness as random

people from here, there,

and everywhere try to bend the

rules of science and suffer the consequences.

We'll explain what

went wrong and why, with the help of sciences

least compromising principles.

Stuff like centrifugal force,

angular velocity,

and that unseen

terror, the vortex.

Please don't try any of

this at home, or even there.

Watch out, it's the

Science of Stupid.

DALLAS (off-screen): In this

episode we'll be looking out for hydrodynamic drag,

look out, balancing our

combined centers of mass over two wheels,

with any luck, and learning

about the strength of trees, but first this.

DALLAS: Whether

rough riding over rolling hills or careering through

wooded glades, a set of two

knobbly tires is your key to access all areas adrenalin.

MAN: Dropping, 3, 2, 1.

DALLAS (off-screen): Although

a knife-edged mountain ridge

is an area I'd prefer

not to access.

When you think you can

take a tumble just peddling in the park,

this does seem like

pushing your luck, and if you don't believe me

just ask him.

MAN: Elland, yo, Elland.

DALLAS: So we're looking at

biking along mountain ridges, whether on motor bikes or

mountain bikes it's a pursuit

that should definitely be left to the pros who will no doubt

appreciate the importance of

such science as normal force.

DALLAS (off-screen):

Friction is proportional to the normal force.

When two surfaces are pushed

together normal force being a contact force acting

perpendicular to a surface.

Riding up a slope, or even

along it, less of the force of his weight is acting

perpendicular to the slope,

so there's less normal force,

less friction and more

chance he'll lose his grip.

Surface structure

is also critical.

If the surface is granular and

crumbly it can be easily sheared away by sideways

forces, and that's no

good for grip either.

DALLAS: Any riders

heading off road should also consider their impact on the

environment and steer

clear of any sensitive areas off the trail.

But as we've seen,

to stay safe riders want lots of friction,

which they can get by avoiding

steep slopes and crumbly rock,

which basically rules out

this entire activity.

DALLAS (off-screen): Err,

that looks a bit steep. How does it feel?

BIKER: Ooo-hoo-hoo-hoo-hoo-hoo.

DALLAS (off-screen): Yeah,

I thought you'd say that.

BIKER: So narrow.

BIKER: Don't look down.

DALLAS (off-screen): I'm

trying not to, but I can't help thinking that surface

looks a bit crumbly.

Yeah, definitely crumbly.

(laughter).

DALLAS (off-screen):

Keeping lined up with the ridge he was okay,

but as his wheel moved

sideways the force applied to the ground overcame the sheer

strength of the

crust, causing it to slip.

MAN: Oh.

(laughs).

MAN: Yeah.

BIKER: Which way

are you going to go?

DALLAS (off-screen):

Well hopefully not down.

Oh.

BIKER: Oh.

BIKER: Oh. Ow.

DALLAS (off-screen): Yeah,

it's crumbly down there too.

So how about we ride somewhere

with a more grippy surface?

A lot more grippy than that.

A crumbly dirt ridge half

covered in snow, not the obvious choice given the

science, but at least we're on

fairly level ground, and now we're on the slope,

and now we're losing friction.

MAN: Come on now, come on now.

DALLAS (off-screen): Okay.

Going uphill less of the force

from your weight is acting perpendicular to the surface,

so less normal force and

therefore less friction.

Apply a little

too much throttle and

your bike becomes

a taboggan.

But once our riders get used

to dealing with reduced normal force and easily shearable

surfaces it's just a matter of

freewheeling it to the bottom to catch up with friends.

MAN: Oh, oh.

MAN: Yes, he's got it.

MAN: Oooh.

DALLAS (off-screen): Oh,

they'll be so glad to see you.

DALLAS: Some things

just don't go together.

Oil and water, petrol and

matches, tequila and fireworks.

So you can imagine my

concern when I heard about a combination of

kayaking and surfing.

DALLAS (off-screen): Then I

saw this and thought, 'Perhaps I'm worrying about nothing,'

and then I saw this and

realized I was right the first time.

DALLAS: Alright, if we're

gonna go treating a kayak like a surfboard we'd better swat

up on center of buoyancy

and hydrodynamic drag.

DALLAS (off-screen): To remain

stable our kayaker keeps his center of mass directly over

the kayaks center of buoyancy,

which is in the middle of its submerged volume.

Traveling out to sea

it helps to keep the kayak perpendicular to the wave,

because turning sideways

can mean more hydrodynamic drag and a salty roll.

When catching a wave

he must ensure the nose doesn't dig into the water,

otherwise the resulting

increase in hydrodynamic drag

could produce a turning effect.

DALLAS: Waves can travel

hundreds of miles, relentlessly building speed

and power before smashing

into your kayak, but we should be okay

providing we remember the rules.

DALLAS (off-screen):

Hold on a minute, should we be perpendicular to the

wave or parallel to it?

Ah yes, it was perpendicular.

By hitting the wave almost

parallel he presents a large surface area,

which leads to

enough hydrodynamic drag to flip the kayak.

We're out and

ready to catch a wave.

MAN: I'm videoing this just

in case things don't go well.

DALLAS (off-screen):

That's a little negative.

MAN: Confident, confident, oh.

DALLAS (off-screen):

But well founded.

Good start, but here

the nose digs in, slows down, and our friends

MAN: Oh, oh, oh.

DALLAS (off-screen):

Enjoy the benefits of the turning effect.

DALLAS (off-screen): Now

these guys have got it.

Nice and perpendicular,

minimal drag.

WOMAN: Ooh.

DALLAS (off-screen): Like a

knife through salty butter.

Maybe it's safer to avoid all

that nasty drag and head out of the surf to calm open sea.

MAN: There it is!

DALLAS (off-screen): Oh look,

a delightful little fish.

DALLAS (off-screen): Can

you work out what scientific principle this dormitory

sledder is going

to demonstrate?

DALLAS (off-screen):

Now, did you guess the science our hallway

roller is about to enjoy?

(laughs).

DALLAS (off-screen): Yes,

that's right, it's impulse momentum theorem.

Impulse is the change in a

objects momentum when acted upon by a force over time.

Less time, more force.

Instead of gently rolling to a

stop, the hard door ensured he lost momentum quickly,

so he experienced more force.

Please, even if your friend is

this insufferable, don't shut the door on him.

DALLAS: And now we turn

briefly from people getting it horrendously wrong,

to someone getting

extraordinarily right.

The next time you're

gridlocked on the motorway watching bikers effortlessly

squeeze between lanes,

consider there may be another option.

DALLAS (off-screen): As

stunt driver, Alistair Moffatt, could prove as he attempts a

Guinness World Record title

for the tightest gap driven through on two wheels.

Those posts are just 78

inches apart, and that is a world record.

DALLAS: On second thoughts,

I recommend you don't try this dangerous stunt on your local

highway, or anywhere else,

because whilst motorbikes operate perfectly

well on two wheels, cars

DALLAS (off-screen): Are

definitely safer on four.

DALLAS: But if you want to

know the science that makes it possible,

buckle up for your physics,

courtesy of our record breaking friend, Alistair.

DALLAS (off-screen):

Alistair builds velocity as he approaches

a specially designed ramp.

This generates just enough

angular momentum to tilt his car to about 50 degrees,

so that its center of mass is

directly over its new much narrower base of support.

As he drives he makes

continuous adjustments with the front wheel,

dynamically moving the base of

support so it remains under the center of mass.

DALLAS: Now then, ramps may be

your professional stunt method of gaining angular momentum,

but some of our wannabe record

breakers have been experimenting by using the

centrifugal force you

get from turning a corner.

Wonder how that's

working out for them?

DALLAS (off-screen): Not great.

Just enough angular momentum

to get on two wheels, but he fell out the side,

which meant the center

of mass suddenly moved the other way and outside of

the base of support.

So how about we stick to a

proper stunt car, or stunt mobility scooter?

DALLAS (off-screen):

The central driving position and low mass

of the mobility scooter

means our man can easily control the combined

center of mass

simply by leaning.

Great style, although you may

have missed a red light there.

(horn).

DALLAS (off-screen):

Yeah, maybe best to take this off the road.

Build a good old fashioned

ramp and get behind the wheel of a proper vehicle.

This looks good.

DALLAS (off-screen): Oh no.

Okay, the positives.

The ramp allows the car to

generate enough angular momentum to get onto two

wheels, and he managed

to keep the center of mass over the base of support.

And the negatives,

it lasted less than two seconds, then he fell over,

somehow rolled back up,

then the car caught fire, then he had another go,

and did exactly

the same thing.

DALLAS (off-screen): Alright,

all of our wannabe stunt drivers were okay,

but I think the

record's safe for now.

Oh, not again. Okay.

DALLAS: Long before

h*m* sapiens, way before the mega mammals,

before the dinosaurs even, the

land was ruled by trees,

around 350 million

years in the making,

trees biology gives us

life supporting oxygen,

and their great strength

makes us feel like idiots.

That evolutionary journey has

spawned over 60,000 tree species and an extraordinary

variety, each perfectly

designed to survive and thrive in its particular environment,

starting from the roots up.

DALLAS (off-screen): A trees

roots absorb water and nutrients from the soil.

Some trees can spread their

roots to three times wider than their height,

anchoring them

firmly into the earth.

The trunk contains vascular

tissues to transport fluid and nutrients,

and ground tissues

with thick cell walls that provide strength

and also a degree

of flexibility.

But if it's subjected to

enough compressive stress, as wood fibers on one side are

squeezed, and tensile

stress, as fibers on the other side are stretched,

its flexural strength will

be overcome and it'll break.

DALLAS: Steadfast, sturdy but

flexible and willing to yield at the right time,

in many ways trees

just seem more advanced than we h*m* sapiens.

MAN: This is going

to be hilarious, this.

DALLAS

(off-screen): See what I mean?

And there's the proof.

MAN: One more go!

DALLAS (off-screen):

Well I don't know.

I mean, that tree might have

an extensive root system so could be very hard to

MAN: Ooh.

DALLAS (off-screen):

No, that's done it.

Once the soil was dislodged

from the roots there was less heavy earth to anchor it,

but thanks to the trees mass

of dense woody tissues it had a lot of weight too.

MAN: Ooh.

DALLAS (off-screen): As that

forklift truck discovered.

MAN: Oh no.

DALLAS (off-screen): I know.

If only you had a machine

that could lift

something heavy, hmm.

Some trees can last thousands

of years, but thanks to its precarious angle and some high

winds, this one is enduring a

lot of compressive stress here and tensile stress here.

Luckily the tree surgeons have

arrived to lower it safely to,

oh for goodness sake.

WOMAN: Yes!

WOMAN: Timber!

DALLAS (off-screen):

Yeah, that's a bad idea.

But whilst less sturdy than

the last tree, this taller thinner tree is more flexible,

so it can bend

without breaking.

MAN: Coming down.

DALLAS (off-screen):

Until it's flexural strength is overcome.

He was okay.

This man has developed

an incredible scientific technique for finding

out if a tree is rotten.

Yep, it is rotten.

He was okay too.

DALLAS (off-screen): When

trees rot, as that one has, the tissues that made them

strong and flexible breakdown,

making it easier to exceed their flexural strength.

But knowing what we

now know about a trees anchoring system,

strength and weight,

it seems wiser to remove them bit by bit.

I said seems.

DALLAS: These days our lives

are made so much easier by gadgets like smartphones,

satnav and the Bluetooth

umbrella, but scientific solutions to everyday problems

aren't a modern phenomenon.

Take the wheelbarrow.

DALLAS (off-screen): For

nearly 2,000 years this simple yet ingenious tool has made

light work of heavy lifting.

DALLAS (off-screen): For those

who appreciate how they work.

And for those who don't,

we open our physics textbooks to chapter three,

class two levers.

DALLAS (off-screen): When a

wheelbarrow is lifted the base of support becomes very small,

and so it requires a lot of

control to maintain stability.

With long handles and a wheel

at one end, a wheelbarrow is

what scientists refer to

as a class two lever.

It's also known as a force

multiplier, as it allows a small force to be converted

into a large force,

meaning heavy loads can be lifted more easily.

DALLAS: It is believed that

the Chinese invented the wheelbarrow around the

second century, revolutionizing

efficiency for their construction workers.

DALLAS (off-screen): And it's

just as popular today in Grimsby, England.

MAN: Come on flower,

you can do it.

DALLAS (off-screen):

Ah, not quite as efficient as the ancient Chinese.

MAN: Brilliant!

DALLAS (off-screen):

Wheelbarrows function well as force multipliers

when you're at

the same level.

MAN: Come on flower,

you can do it.

DALLAS (off-screen):

Otherwise they work better as humiliation multipliers.

MAN: Brilliant!

DALLAS (off-screen):

At least it's only soil.

This chaps

pushing horse manure.

DALLAS (off-screen):

And now he's wearing it.

Slipping on the ramp, he

actually turns his class two lever into what scientists

refer to as a class one lever,

or what we call a teetertotter.

DALLAS (off-screen): But keep

your barrow at ground level and you'll be fine.

Unless you're riding in it.

Driver lifts too high,

wheel guard hits ground.

Force multiplied.

DALLAS: Standard two-armed

cartwheels, near-armed cartwheels,

far-armed cartwheels,

one-armed cartwheels, no-armed cartwheels,

quarter-turn-out cartwheels.

To the gymnast cartwheels are

the gift that keeps giving.

So wouldn't it be nice to

have a friend to join in?

DALLAS (off-screen): Well as

luck would have it there's a two-person cartwheel,

but if that seems a little

tricky for the non-gymnast, here's another slightly less

official method for

two pals to get in on that rotational fun.

It's still a bit

tricky though.

DALLAS: So that's two ways

that two can spin, two ways of impressing your friends,

two ways of doing yourself an

injury, two ways of swatting up on your angular velocity.

DALLAS (off-screen): In this

example one gymnast generates only enough angular velocity

so they land with their

combined center of mass over their base of support.

Whereupon the other pushes

back to generate enough

angular velocity

to counterrotate.

In the second version, our

gymnasts generate enough angular velocity to keep the

rotation going, whilst

gripping tightly to keep their combined center of mass

central to the rotation.

DALLAS: Alright, so let's

start with our first example, the waist hold.

Remember how that works?

MAN: Like that? Or like that?

MAN: How do you do it?

DALLAS (off-screen):

Go on lads, it doesn't matter which way round,

just focus on

getting enough angular velocity for the rotation.

MAN: 1, 2, 3.

DALLAS (off-screen):

That, as you may have deduced, was not enough.

This chap didn't push off

enough, so their combined center of mass was nowhere

near being over their base

of support when they landed.

Ah well, it's a good

excuse for a friendly cuddle.

Loads of angular velocity

DALLAS (off-screen): Except

for the last bit, and that lack of rotation meant

she couldn't get her legs

underneath, and so he basically threw her on her

back, then landed on top.

Not quite a perfect

ten, but progression.

So we graduate to the official

proper two person cartwheel.

Oh yes.

DALLAS (off-screen):

Stunning angular velocity, combined center of mass,

nice and centrally positioned,

and for a final flourish,

half a roly-poly and

jazz hands, classic.

DALLAS: Cosmologists have

often pondered whether our universe is just one of an

infinite number of universes

where infinite versions of ourselves live out the

infinite possibilities

of our existence.

Who knows, but we can't

all be making the same mistakes can we?

(music plays through credits)

♪