08x14 - Kite Surfing, Rollerblading and Compressed Air

[bunniefuu]

DALLAS (off-screen): This

is the Science of Stupid.

Yes, this is the show that

finds the science hidden in

the stupid.

Watch as the scientifically

ignorant discover what the

rest of us already know

that physics always wins.

We'll study what went wrong

and why with the help of

scientific principles

like terminal velocity,

hydrodynamic drag and,

series favorite,

axis of rotation.

Take on science at your own

risk, you have been warned.

It's the Science of Stupid.

In this episode we'll be

discovering how you can use

kinetic energy to get

more room in the bed.

We'll be learning the

advantages of angular velocity,

the hard way, and

giving you a master class in

how to start kite surfing,

or at least how

not to but first this.

Shopping during the sales

is a competitive business,

to win you go in hard and don't

let anything get in your way.

How much for the pink dress,

the one with the tire mark?

Where our keen bargain hunter

has gone wrong was that she

hadn't mastered the art of

acceleration and deceleration

on her scooter, and it's not

surprising because it's not

just an art.

It's a science.

Turning a scooter's throttle

delivers extra power to the

wheel, allowing

it to accelerate.

Braking applies friction to

the wheels which causes the

bike to decelerate.

Sufficient friction between

the tires and the road is

essential for acceleration

and deceleration,

and as long as the rider

is holding on tight enough

they'll act as one unit but

if they do become separated

inertia will try to keep the

rider moving in a straight

line, regardless of

what the bike does.

So, it's throttle

to accelerate,

friction at the brakes to slow

down and friction at the road

to make the first

two possible.

Oh and whilst crashing can be

a faster way to stop it's not

an advisable method.

Okay, science learnt.

Let's go shopping.

For a new fence.

This nervous rider, hiya.

Appears to know where the

throttle is but doesn't seem

to know how to steer

or use his brakes.

Putting his foot down doesn't

provide as much friction as

braking would have but luckily

the fence provided all the

deceleration he needed.

Thankfully he wasn't

traveling fast.

Unlike him.

As we learnt, it's best to

decelerate using the gradual

friction method, i.e. brakes,

and not the impact force

method, i.e. crashing.

The flexibility of the barrier

reduced the impact force

experienced by the rider but

it still looked painful.

There's no barriers here,

except that one.

Our rider hits the brakes but

there's insufficient friction

between his tires and the

road so he skids and can't

decelerate in time.

So, the car applies a

force to his scooter,

rapidly decelerating

it but not him.

Thankfully both drivers were

fine and they each learnt a

valuable lesson about inertia.

So, as long as you

remember, throttle control,

braking rather than crashing

and maintaining good contact

with the road a

scooter is your friend.

But not his.

Now then, this is the point in

the show where we take a break

from the ill-advised and look

at the truly magnificent,

and you can't get more

magnificent than this.

These wheelchair athletes are

going to try and set a new

world record by pulling these

three trucks weighing an

incredible 110,407.5 pounds

over 328 feet.

And that is it.

A new world record.

Well done, team.

The reasons this team could

achieve this amazing feat were

dedication, drive,

physical prowess

and a mastery of inertia.

To tow an object you need to

apply a force large enough to

overcome its inertia, which

is proportional to its mass.

Friction between the object

and the surface can make

towing harder but adding

wheels provides rolling

friction, which offers

less resistance,

and the puller or pullers need

friction with the ground to

get a reaction force to

move the object forwards.

Apply enough force to overcome

an object's inertia and make

sure the friction isn't too

high for the thing being

pulled or too

low for the puller.

Alright, which of our trainee

record breakers can put the

aforementioned

theory into practice?

Not that one.

Our muscly friend applies

enough initial force to

overcome the heavyweight

inertia and friction with the

ground until the strap breaks.

So, how do we

make this easier?

Oh, maximum science

points, Dad.

Snow, low is the friction

between the ground and the

mass he's towing, or children,

allowing him to easily

overcome their inertia.

Of course, there is another

way of making that easier.

MAN (off-screen):

Watch the tree.

DALLAS (off-screen):

Oh! Yes, that's right, Dad.

By losing mass.

Okay, let's forget the

snow and try some wheels.

Lots of wheels.

MAN: Oh.

DALLAS (off-screen): Lots

of wheels but not helmets.

The cyclist can easily pull

the skateboard as its wheels

give it low rolling friction

but when he leans too far back

and his center of mass falls

outside of his base of support

the wheel's low rolling

friction causes the board to

fly forwards and him

to stop for a snack.

MAN: He ate the kerb.

DALLAS (off-screen):

Speaking of snacks.

Our friend here can pull the

heavy fridge because his

bike's grippy tires create

enough friction with the road

whilst the casters under

the fridge provide rolling

friction, which offers

little resistance.

I don't know what

you're looking at mate,

we all get a bit

peckish when we cycle.

So, there you go, breaking the

vehicle towing record is all

about overcoming inertia.

And occasional dogs.

I'm sure we've all got one of

these corn strippers at home

but can you guess what science

this young cob spinner wants

to demonstrate?

DALLAS (off-screen): Now

then, did you work out the scientific principle he was

keen to show us?

Yes, it's torque.

By applying force at distance

to the axil the young corn

enthusiast can produce a large

amount of torque to turn the

machine, however when he steps

too close and the handle gets

underneath him the momentum

of the machine applies enough

torque to overcome his weight

and take him for a ride.

Maybe just buy it

in a tin next time.

I love kites and I love

surfing so I thought to

myself, "Why not

learn kite surfing?"

What's not to love?

Apart from that.

It turns out that even just

learning to control that kite

on the beach is

complicated enough,

so how about a crash

scientific course on the

basics of kite surfing?

Starting with what

kite surfers call

the "wind window."

The wind window is a

three-dimensional arc of sky

downwind of a surfer in which

the kite is able to fly,

directly downwind of the

surfer is the power zone where

the kite generates

maximum power.

At the edge of the window the

kite produces the least amount

of power.

Whilst water offers low

resistance to movement the

surfer experiences increased

resistance from the land,

which combined with the power

from the kite generates a

large turning effect,

which he should lean back

to counteract.

To help them keep control kite

surfers are taught to launch

their kites at the edge of the

wind window where they won't

be hit with an

overload of power.

Sounds simple enough but it

takes quite a lot of practice.

This young scientist is

learning kite control on the

edge of the power zone.

MAN: Oh.

DALLAS (off-screen):

Learning, not learnt.

As he dives the kite into the

power zone its power increases

substantially and he

can't resist the pull.

Thankfully his friends

were there to help

and by "help" I am of

course being sarcastic.

Let's try with two

people holding, shall we?

MAN: No, no!

DALLAS (off-screen):

See, much more secure.

Where's she going?

MAN: Are you alright?

WOMAN: Yeah.

DALLAS (off-screen): The kite

was launched directly into

the heart of the power zone,

so it generated more power

than she could keep up with.

Lesson learnt.

MAN: Whoa, whoa, whoa.

DALLAS (off-screen): Oh,

she's off for an ice cream.

Water offers less resistance

to motion than land so he can

take advantage of

the pull of the kite.

MAN: Agh.

DALLAS (off-screen):

Until he hits land again.

Next time keep an

eye out for terra firma

and unexpected sea dogs.

Close one.

When it comes to crossing

rivers some people prefer

boats, others bridges.

Personally I find both boring,

I much prefer stepping stones.

They're much

more fun to spectate.

Our friend there broke the

first rule of stepping stone

stepping, that is to

ensure that the stone,

or platform to be

stepped on, is sturdy and not floating about.

He also broke pretty much all

the other rules as set out by

the following

scientific steps.

The stepping stones must

be dry enough to provide

sufficient friction to

prevent him slipping.

He must land with his

center of mass close to his

base of support,

this ensures his

feet do not apply too much

horizontal force, which could

risk overcoming friction with

the stepping stone.

Lastly, even shallow slow

running rivers can be

deceptively dangerous places.

So, another critical rule

is to check that the body of

water and crossing platforms

have been designated as safe

by the relevant authority.

Alright, science

taught but was it learnt?

No.

To start with the river is

fast flowing and clearly

dangerous, the angle of

the scope made the launch

difficult, the low friction

between his feet and the mud

made is non-existent.

Where's your phone?

Oh, ah.

He's like a mountain goat,

a mountain goat that's

just fallen into a river.

When he lands on the last rock

his center of mass is too far

behind his base of support,

so his feet applied a large

horizontal force which

overcomes the friction the

rock can offer.

Luckily the fall was broken

by the ice cold raging torrent.

Okay, it's flat.

MAN: Come on, man!

MAN: It's not that easy.

DALLAS (off-screen): Relatively

dry and it's a small gap.

We've got this.

Yes, yes.

No.

MAN: Oh my goodness.

DALLAS (off-screen):

No, we haven't.

He made the jump but due

to his heavy backpack his

center of mass is, again,

behind his base of support

and so he falls backwards.

Grabbing the branch would

have been a good idea if it had

been attached to something.

This adventurer's not even

bothering, he's just wading,

unlike his friend

who's swimming.

It's only a small step but

the landing stone has been

lubricated by the

water so has a very low

coefficient of friction,

almost as low as his face.

DALLAS: Air is a remarkable

substance, not only does it

allow us to breathe,

which I think we can all agree is a good thing,

but if you compress it and

contain it you can have loads

of fun.

Like defying

the laws of physics

or for whacky furniture.

Whack, see.

The secret to understanding

and using compressed air is to

realize that all it wants to

do is stop being compressed air.

It wants to escape and in so

doing air teaches us valuable

science on

pressure differentials

and conservation of energy.

If air in one part of a

container is compressed it

will apply pressure to all

other parts until all areas

are the same pressure, this is

due to conservation of energy.

When a container of compressed

air is open to the atmosphere

the high pressure inside

equalizes with the lower

pressure outside, producing

a force as the air escapes

and whatever is containing

the compressed air needs to have

the material strength to

withstand the pressure

differential,

otherwise it will fail.

To sum up, pressure changes

will be transferred to all

parts of the container, give

something at high pressure an

opening and it will take

it and escape with force,

and finally whatever you do

make sure the container you're

using is strong enough.

So, now you know but

do our researchers know?

WOMAN: Don't break my bed!

DALLAS (off-screen):

Yes, they do.

The jumper has cleverly

demonstrated a basic

pneumatic system.

He adds kinetic energy

with his jump which causes a

pressure change in the bag and

due to conservation of energy

the kinetic energy is

transferred to her and she

then transfers that same

energy to the bedside table

via her head.

MAN: Are you OK?

DALLAS (off-screen):

How about something a little more high tech?

Surely these

amateur rocket engineers

understand pneumatics.

Ah, turns out they don't.

The young researcher was

trying to compress air by

jumping on the pump.

Unfortunately he misses.

WOMAN: Oliver!

DALLAS (off-screen):

But Oliver doesn't.

When the pump is pressed the

pressure differential created

applies a force that

launches the rocket.

WOMAN: Oliver!

DALLAS (off-screen): Good to get

a closer look at the physics.

Understanding the science

allows you to take advantage

of the science, like

building a beach trampoline.

Fun times.

MAN: Oh.

DALLAS (off-screen):

Yeah, less fun times.

The membrane of the beach

ball didn't have the material

strength to contain the higher

pressure produced by our more

short-footed researcher.

We can all use science

to elevate the ordinary.

A case in point, you could

just rollerblade or you could

use angular momentum to add

a little something extra and

make it a bit special.

You see. Special.

Now, what our young friend was

attempting was a rollerblade

flip and the reason he failed

was that he hadn't studied

angular momentum,

angular velocity or even

moment of inertia.

Luckily you can.

First he needs sufficient

take-off velocity for enough

height and air time

to perform the flip.

As he launches he leans to

generate angular momentum.

He then tucks in, decreasing

his moment of inertia,

which increases his

angular velocity,

meaning he spins faster

and completes his flip.

Angular momentum, the momentum

you have when you're spinning

cannot be changed

once you've launched.

Angular velocity, your spin

speed, can be changed mid-air,

as we've seen by

tucking in or decreasing

your moment of inertia.

Get all that right and you

can flip backwards or forwards.

Whether you want to or not.

(screams)

This skater wasn't trying to

add a flip but his one-foot

take-off gives him

unexpected angular momentum and

an unintentional

90-degree rotation.

MAN: Ow.

DALLAS (off-screen): Now,

this researcher is trying to

add a flip.

But he probably

wishes he hadn't.

He doesn't tuck in to reduce

his moment of inertia and so

doesn't have sufficient

angular velocity to complete

the turn but if he wanted

to smack his back on the floor.

It was textbook.

MAN: Oh.

DALLAS (off-screen): That's

better but that's worse.

Even though he had good speed

at take-off he holds his tuck

too long and so has too

much angular velocity.

He should have extended his

body earlier to increase his

moment of inertia

but instead he just extended

his dental work.

MAN: Oh.

DALLAS (off-screen): Okay,

good speed, great spin.

WOMAN: Yes.

DALLAS (off-screen):

Just the finish to go.

MAN: Yeah.

DALLAS (off-screen): Yeah, he

definitely meant to do that.

And that is it.

We have run out of time but

unfortunately not stupidity.

So, please do not copy any of

the dangerous stunts you have

just seen.

As Bill Nye the

Science Guy once said,

"Science is the best

idea humans have ever had."

Sorry Bill, I guess

this lot missed that class.

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