08x15 - Towing, Swinging and Tumbling.

[bunniefuu]

DALLAS (off-screen): This

is the Science of Stupid.

Yes, this is the show that

gleans scientific wisdom

from sheer stupidity.

Observe as adults

and future adults

take on the power of physics

and come off second best.

We'll reveal what went wrong

and why

with the help

of scientific principles

such as buoyancy,

angular velocity,

and centrifugal force.

So, watch but never

imitate because this

is the Science of Stupid.

In this episode,

we'll be examining

the stability of towed boats,

getting to grips

with pendulums,

and looking at torque

in water skiing.

WOMAN: Bend your knees!

DALLAS (off-screen):

But first this.

The electric light,

the telephone, the microchip,

all great inventions but for

me the most important of all

was the wheel, mainly because

it led to things like this.

Downhill cycling

and why use two wheels

when one makes you

look twice as cool?

But before you even think

about pulling off

a downhill wheelie

be aware that

even on two wheels.

(screams)

It can still be perilous.

What makes downhill cycling

such a terrifying pursuit

is that the bike isn't only

powered by the cyclist's legs

but also by our

old friend gravity.

When a cyclist goes up

a hill he gradually gains

gravitational

potential energy.

When he descends this

gravitational potential energy

can be converted over

a very short period of time

into a terrifying amount

of kinetic energy.

If the rider falls,

that kinetic energy

might be converted

into heat via friction,

or if they stopped suddenly

dissipated by deformation.

So, energy is never destroyed,

it's merely transferred

into something else

like kinetic energy,

heat, or even the sound

of an impact,

which is often accompanied

by the sound of screaming.

To investigate

we sent out some of our more foolhardy researchers.

This guy has made a deal with

gravity and built up a lot of

kinetic energy, so much so

that he's able to pass cars,

except that one.

The cyclist is unable to

transfer enough kinetic energy

into heat via

friction at his brakes.

When he hits the car his

remaining kinetic energy is

transferred into sound,

heat and dissipated via

deformation, also

known as bouncing off.

Don't worry, he was okay.

Alright, let's

try a gentler pace.

This is more like it,

a chance to take in the scenery.

And his friend's bottom.

He appears to make no attempt

to reduce his kinetic energy

and his linear momentum

becomes angular momentum as he

rotates around the

axle of the front wheel.

MAN: Oh dear,

first crash of the holiday.

DALLAS (off-screen):

And maybe not the last.

Perhaps it's safer to go

downhill on three wheels with

these drift trikes.

Or maybe not.

It's just as well our drift

trike g*ng are heading home

on four wheels.

It may be safer just to walk.

Water skiing is hard,

water skiing bare foot is even

harder but water skiing bare

foot whilst performing tumble

turns, well that's better left

to experts like Greg Sample.

Yup, we're turning our back

on failure for a moment to

celebrate brilliance

and it doesn't

get much more

brilliant than

Greg from the US.

He's attempting a

Guinness World Record title

for the most barefoot

tumble turns in one minute

and 33 is a new world record.

Oh, Greg's let himself go.

Greg makes it look easy but

then he's put in the time and

the practice.

Alas, for every Greg there's

a load of wannabe record

breakers who feel

they don't need to.

Let's see if they're right.

(screams)

Nope, I didn't think so.

Attempting to water ski

bare foot can be painful,

so if you're lucky enough to

own a boat please don't try

this without proper

instruction but how do the

pros like Greg pull

off that perfect tumble?

The skier angles his feet

up deflecting the water

downwards, which creates an

equal and opposite reaction

force pushing him up.

There's a torque,

or turning effect,

generated from the distance

between the pull of the boat

and hydrodynamic drag

from the water at his feet.

Bending the knees helps absorb

the impact of any bumps in the

water and keeps the center of

mass safely behind the feet to

produce enough torque in

the opposite direction to

counteract the turning effect.

To perform the tumble turn he

shifts the handles so the pull

from the rope is to the side

of the drag from the water,

generating a torque

that spins him around.

So, equal and opposite

forces, Newton's Third Law,

hydrodynamic drag and

torque are all key to breaking

this record.

But just getting on the

water is also fairly important.

MAN: Go, go.

DALLAS (off-screen): Let's go to

the next wannabe record breaker.

MAN: Woo-hoo.

DALLAS (off-screen): This lady

has enough speed to create a

reaction force to keep her up

but she's forgotten one key

bit of science.

WOMAN: Bend your knees!

Bend your knees!

DALLAS (off-screen):

That's the one.

With her knees locked she

can't react to the bumps in

the water so her feet dig in

and a sudden increase in drag

turns her linear momentum

into a face plant.

WOMAN: Bend your knees!

DALLAS (off-screen): Now

she's been paying attention,

she's got her legs bent

and we're looking good.

Of course, whilst attempting

an energy-sapping tumble turn

it's important

to keep hydrated.

But it's even more important

to A, not drink beer whilst

bare foot skiing and B, focus

on what you're doing so you

don't end up accidentally

dipping your toes in and

getting a sudden increase

in drag from the water.

She did get hydrated

though, by the lake.

Our last challenger is

deflecting the water well,

that has a good body posture.

It's tumble turn time.

There's the sort of turn.

And that's

definitely a tumble.

That turn won't

win any prizes,

then when he transfers his

weight back onto his feet too

fast the drag from the water

combined with the pull from

the rope makes him

flip but full marks

for trying to hang on.

I think Greg's

record is safe for now.

This guy is showing off his

best hydro jet moves but can

you guess the

scientific principle

he is about to demonstrate?

DALLAS (off-screen): Now, did

you guess the science this man's

hydro jet display would lead to?

That's right, it's thrust.

The water coming out of the

jet nozzle produces an equal

and opposite

force known as thrust,

this keeps him in the air but

when he holds onto the railing

the rail acts as a pivot

and the thrust rotates him.

(screams)

Oh, science you rogue.

When I was a lad we

didn't have games consoles,

the Internet or basically

anything good but what we

could always rely on for

entertainment was some old

rope and a tree.

What more could

you possibly want?

Well, someone to push

you was always a bonus.

Take it away, Dad.

My dad was like that too.

Aside from pushy dads there

are other things we need to

consider in order to get the

most out of a tree swing.

The swing and swinger

combine to form a pendulum.

The swinger's mass and velocity

means they have momentum.

This is greatest at the bottom

of the swing where they're

traveling the fastest.

The swinger's momentum applies

more downwards force to the

tree swing than the force

of their weight alone.

If the total force exceeds the

flexural strength of either

the seat or the branch, or

their center of mass falls

outside their base of support,

gravity could get its way.

So, while more momentum equals

more fun it also equals more

potential for pain.

Let's see if our

researchers have done their

science homework.

Being fixed at a single point

allows the tire swing to act

like a three-dimensional

pendulum swinging her

in all directions.

Including into the treehouse.

The rope intersects with the

corner of the tree house,

tilting the tire

putting her center of mass

outside her base of support.

Perhaps it's best to swing

without someone pushing.

MAN: Hashtag

bring down the broom.

MAN (off-screen): Bring down

the house. Whoa. Oh, yeah. Oh.

DALLAS (off-screen): Hashtag try

to avoid additional passengers.

In this experiment it was the

mass and downwards momentum of

the extra swinger that

overcame the flexural strength

of the branch,

causing it to snap.

That branch looks sturdy and

her friends are merely there

to help her demonstrate how

the momentum she gains will be

effected by the

height she swings from.

MAN: One more for luck.

WOMAN: Oh my God. Oh!

DALLAS (off-screen): Well,

that's cleared that up.

Near the top of the swing

she had little momentum,

by the bottom she had lots

and whilst the branch she was

swinging from was sturdy, the

branch she was sitting on was

basically a twig.

So, the best idea is to avoid

all that momentum and find a

nice sturdy place to sit down,

like the ground.

Solubility is a measurement of

how much of a substance will

dissolve in a given

volume of liquid.

If a substance

dissolves it's soluble,

if it doesn't it's insoluble.

Some examples.

The sugar in their cake mix

is soluble in water and will

blend in but her hair is not

soluble and will not blend in.

And he isn't soluble

either, no matter how much

they mix him.

Okay, why are some things

soluble while others aren't?

Well, a substance's

molecular polarity is key.

Sugar is soluble in water,

this is because both water

molecules and sugar

molecules are polar,

meaning they have a difference

in charge across them,

thus are attracted

to each other.

So, the water molecules form

intermolecular bonds with the

sugar molecules separating

them from each other so that

the sugar eventually

becomes too small to see.

Polystyrene comprises

of non-polar molecules,

it's not soluble in water but

it is soluble in similarly

non-polar solvents,

like this acetone.

A substance's solubility

can have a dramatic impact,

for example where water

dissolves soluble bed rock

underneath roads.

Which may have been the

cause of this sink hole

and from car eating

holes to a salt eating man.

The positive and negative ions

in salt are attracted to the

polar water molecules

in his soup,

so they dissolve and disappear

unlike the revolting taste.

But solubility can be a life

saver for this young artist.

MAN: Explain to Mom.

WOMAN: Wait, what happened?

BOY: Um.

DALLAS (off-screen): Quick, think kid. Think.

BOY: The monster

did this last time.

DALLAS (off-screen): Perfect.

MAN: See if it

will come off the wall.

DALLAS (off-screen): Luckily

for the monster this paint is

water based so it can form

intermolecular bonds with

water molecules and will wash

off with a little scrubbing.

Did you know that a little

solubility knowledge can come

to the rescue if you

swallowed a hot chili?

Drinking water doesn't

actually help because

capsaicin, the chemical

that makes chilies hot,

is insoluble in water

therefore the water

can't wash it away.

So, what can?

MAN: One, two, three.

DALLAS (off-screen): Well,

let's say you were to munch on

an extremely potent

and potentially dangerous

ghost chili.

You'd experience

this kind of thing.

MAN: Help me!

It's gone up my nose

and my nose is burning.

DALLAS (off-screen): Now,

milk contains a substance

which dissolves the capsaicin

and helps wash it away.

MAN: It's getting worse.

DALLAS (off-screen): Okay, it

hasn't worked yet but sometime

soon hopefully and that was

your lesson in solubility,

and some things.

MAN: Ghost chili.

DALLAS (off-screen): You should never ever do.

MAN: Ah see you later.

DALLAS: Now, I love a bit

of boating but I don't love

getting the boat to the water

because boats are large,

awkwardly shaped objects

not designed for road travel.

Unless your boat

is a car, of course.

MAN: Don't see that every day.

DALLAS (off-screen): No.

And that's because

most boats aren't cars.

They're boats and towing one

to the water in a car can lead

to all sorts of

science-infused issues.

Boats can be quite heavy and

can have a high center of mass

when put on a trailer.

When you turn a corner

centrifugal force acting on

that relatively high center of

mass can generate a sizeable

turning effect.

If the base of support,

the trailer's wheels,

is insufficient this turning

effect will be enough to lift

the inside wheel and cause

the boat and trailer to roll.

So, science learnt.

Let's examine the three stages

to make it to the water.

Stage one, before setting

off make sure your boat

is properly attached

to your vehicle.

Did I mention it was

heavy in the science?

Stage two,

watch out

for hidden obstacles.

Hitting a pot hole causes

the trailer to swing sideways

and that high center of mass tips

beyond the base of support.

And finally, stage three.

MAN: There it goes.

DALLAS (off-screen):

Use an appropriate trailer.

MAN: What did I tell you?

DALLAS (off-screen): I think

you were probably telling us

that on a corner

the centrifugal force

creates a turning effect

which the base of support

of the trailer

is nowhere near wide

enough to resist.

Luckily, the inflatable

side of the boat

causes it to bounce back.

MAN: Oh, that is awesome.

DALLAS (off-screen):

No, it's science.

Since the dawn of time humans

have liked to show off their

strength and there are few

better tests of might than the

aptly named muscle up.

All you need is a bar.

Available at all decent

children's playgrounds.

Some technique

does help though.

While you don't have

to take your top off

to perform a muscle up,

it does require

a lot of upper body strength,

in fact the most

consecutive muscle ups

on a bar is only 26.

Right, let's get

down to the science.

First, he needs a good grip

on the bar

which has enough material

strength to support him.

Once on a pendulum motion

called "kipping"

gives the body

a little momentum,

followed by

an expl*sive contraction

of the shoulder's

lat muscles

accelerating the body upwards.

While the body

has upward momentum,

the hands move

into a new position

and the triceps

and the front shoulder muscles

contract to lift the body

until the arms

are fully extended.

He then uses his muscles

for a controlled descent.

Basically, there are a lot

of muscles involved,

we sent our strongest

researchers out

to test the science.

This lifter has

just enough strength

for a clumsy muscle up.

It's just unfortunate

he didn't spot the fan.

He starts off okay

but pauses once up,

meaning he doesn't use

his upwards momentum

for the second part

of the lift

and probably wishes

he'd given up at that point.

Perhaps it's best to perform

muscle ups somewhere

with plenty of head room.

Like outside.

He's got enough momentum

with his kipping

and up he goes.

And down he goes.

He's got a great technique

but it's the lack

of material strength

of the fixing at the side

that's let him down.

Let's raise the bar a little

and try the rings.

MAN (off-screen):

Turnover. Yeah.

DALLAS (off-screen): The rings

are even harder than the bar.

The flexibility of the rings

provides little resistance

so his wrists

rotate 180 degrees.

MAN (off-screen): Yeah.

DALLAS (off-screen): Making

this more of a muscle down.

Okay, let's get back

on the bar

and lower it.

That looks painful,

sounds painful too.

And that's it, that's all the

science we've got time for

but as astrophysicist

Neil deGrasse Tyson once said,

"The good thing about science

is that it's true whether or not you believe in it,"

and these guys

prove he's right.

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