06x09 - BMX, Ice and Log Walking

[bunniefuu]

[Dallas off-screen]
This is the Science of Stupid.

Yes, this is the show where absurdity
and insight

face off dressed in lab
coats.

Prepare yourself to see renegade
risk takers gamble it all

in the pursuit of
scientific knowledge.

[man] Oh.

[Dallas off-screen] Then
we'll show what went wrong.

[man] Ah.

[Dallas off-screen] And why

with the help of fundamental concepts of
science like

gravitational potential
energy, granular material.

[man] Oh.

[Dallas off-screen]
And flexural strength.

In the w*r between science and stupidity
you have to choose sides,

so don't be a loser,
pay attention.

It's the Science of Stupid.

In this show we'll be learning
all about negative feedback,

ground reaction
force and curvature

but first this.

We all know the feeling,

you've mastered the turn down, can do
the double peg with

your eyes closed and you're wondering is
there anything in the world of

BMXing left to challenge me?

Well, welcome
to the front flip,

it's a crowd pleaser
but a quick word of warning,

mastering this one
is going to hurt.

Front flips are considerably harder than
backflips

because you need to land
blind.

It goes without saying that you
shouldn't be doing this

unless you're in the right place with
the right kit,

but if you do want to add
this trick to your BMX routine

you'll really want to pay
attention to this science.

Our rider launches at a steep angle and
with considerable velocity

so he can achieve a high parabolic
trajectory.

On launch he throws his weight towards
his front wheel

to initiate forward
rotation,

then he brings in his arms and legs to
reduce his moment of inertia,

which increases his angular velocity to
make it all the way round.

So, that's how but if I could add one
more piece of advice

it would be if you're gonna do this,
you really need to commit.

Changing your mind half way isn't gonna
do you any favors.

See what I mean?

[man] Are you OK?

[Dallas off-screen]
High launch angle, check.

Forward lean on
take-off, absolutely.

Bringing in limbs close to the bike to
increase rotation, err, not even a bit.

[man off-screen] Oh, no.

[Dallas off-screen] He still made the
flip

but not quite in the way he'd
probably planned.

[man] My head...

...******* hurts!

[Dallas off-screen] Yeah
and I think I might know why.

Let's see if this next
guy does any better.

[man] Justin Finger
from [inaudible], yeah.

-Oh.
-[Dallas off-screen] Well, no

but he does
get it wrong in quite a funny way.

This BMX bandit doesn't know much about
keeping his shoes on and even

less about parabolas.

His launch angle has no horizontal
component,

in other words he was coming
down on

the wrong side of the ramp
no matter what happened.

And there goes his shoe.

[man] Oh.

[Dallas off-screen]
Still, nice come back.

[man] He's got it!

[Dallas] Yeah, this is obviously
harder than I thought.

Maybe it's one of those things that's
better left to the professionals.

Like this guy because when the crowd's
behind you, you can do amazing things.

But that doesn't
always mean that you will.

This stuntman had enough angular
momentum for a double flip

but his front
wheel was

slightly twisted on landing, so it acted
as a brake giving the rider

that little bit more
rotation than he wanted.

I've heard it said when Alexander the
Great was 33

he cried salt tears because
there were no more worlds to conquer.

[man] Yeah.

[Dallas off-screen] Andy Buckworth is
just 27 and he's mastered the

double front flip, so
who who's great now, Alex?

[man off-screen] Yeah.

[Dallas] It's a
funny thing, ice.

Unusually for a solid it's less dense
than its liquid counterpart,

look it's floating, and while we tend to
think of ice as being just one thing,

there are actually several types of
water ice known to science.

In the year 2000 an iceberg
broke off from Antarctica

with a surface area with
over 4,100 square miles.

[man] Oh my God.

[speaking in native language]

[Dallas off-screen] That's about the
same as Jamaica

but quite a lot
chillier.

[speaking in native language]

[Dallas off-screen] This one is
a mere ice cube by comparison.

[man off-screen] Whoa.

[speaking in native language]

[Dallas off-screen] In fact, seasonal
snow and ice can cover up to



In places like Canada it gets cold
enough for bubbles to freeze over

or to use lakes as roads.

Just eight inches of ice should be
enough to drive on but this ice is

a little thinner than that.

And you guys are walking home.

As water cools its molecules
have less and less energy.

Once they hit 32 Fahrenheit
they begin to arrange themselves

in a rigid
structure and form ice.

When oceans begin to freeze small
needle-like ice crystals

called 'frazzle' form.

The crystals expel
the salt as they grow,

meaning sea ice is
composed of fresh water.

We find ice hard to walk along as it has
much lower friction than normal ground.

This means you can't apply much lateral
force before your foot starts to slip,

like that.

To successfully walk on ice you'd do
well to take a lesson from penguins,

your best bet for staying up right

is keeping your center of mass
low over your

front leg and taking small steps to
minimize lateral forces.

It doesn't always work.

In Alaska the Iñupiat people have more
than 100 names

for different types of
sea ice and

that's because ice acts in many strange
ways depending on the configuration

of its crystals.

Even a small chunk can
be surprisingly solid.

[man] ******* hell!

[Dallas off-screen] And that weird noise
is softly packed ice slowly approaching.

This is an ice shove or ivu.

A constant wind is blowing thousands of
tons of lake ice on shore.

[woman] This is crazy!

Look at this!

[Dallas] It might not be quick.

[woman] Nicky, it just busted
through a door over here.

[Dallas off-screen] But
it can still be a problem.

[woman] Look at that.

It's going right through
their ******* house!

[Dallas] I know what you're thinking,

"I don't live anywhere near a lake so
why do

I need to worry
about ice shoves?"

Well, you probably don't but you may
need to worry about icy sidewalks.

By holding her shopping bags low

this lady has lowered her combined
center of mass

but it doesn't seem to have helped.

Ice's low friction means that it's very
hard to take a step

without a small
lateral force causing a slip like that.

Oh, good.

Someone stopped to help.

Oh, that's what he does
for the rest of the year.

[man] Are you ready for this?

A little half court
shot going that way.

[Dallas] What science is this
basketballer about to show us?

[man] Are you ready for this?

[Dallas off-screen]
We asked you what science

this basketballer
was about to demonstrate.

[man] Nope...that way!

[man] Ah, my [bleep].

[Dallas off-screen] There's a lot going
on here but in a nutshell

it's angle of reflection.

[man] Nope, that way.

[Dallas off-screen] The ball was thrown
at too vertical an angle

and as things bounce back
at approximately the same

angle to the vertical
as they hit, well,

let's just say his trick shot.

[man] Ah.

[Dallas off-screen] Was
more entertaining than planned.

[man] My [bleep].

[laughter]

[Dallas] People nowadays seem obsessed
with teambuilding exercises

and trust falls are all well and good

but if you really wanna know who's got
your back then get your office

to try synchronized flips.

Good work, chaps.

As my grandmother used to say,

the team that flips together runs a
tight ship together.

But, of course, there's
one person in every group.

That just isn't a team player.

There are many things that make
synchronized flips difficult,

one is obviously finding a safe
place to do them

but the even bigger problem is
the fact they require other people.

As our athletes push downwards
they create a reaction force

from the ground to
launch themselves up,

throwing their weight backwards before
leaving the ground provides

the angular momentum needed
to complete the rotation.

The taller jumper needs to launch with
greater force in order to stay in sync

with his partner.

And it's worth remembering that because
they're linked

staying in alignment is
vital.

If they're out of sync then
the person lagging behind

will provide torsional dampening to

the jumper in front, creating an
opposing torque and making it very,

very hard for either of them to come out
of this looking cool.

And let's face it, that's pretty much
what this is all about.

If you look up cool in the dictionary,
you'll see these guys.

[gasps]

[Dallas off-screen] Right under
antonyms, it means opposite.

The guy in the orange T-shirt is a bit
larger than his friends,

so he needs to push with a larger ground
reaction force to get around in sync

with the others.

He doesn't so.

Err, he doesn't.

Remember, stay in sync.

[woman off-screen] Oh, Keifer.

[Dallas off-screen]
Or your neck will kink.

One of these guys doesn't even try to
flip

but that means he becomes a major
torsional

damper to his
friends either side.

Slowing their spins and ruining an
otherwise lovely day out.

[woman off-screen] Oh, Keifer.

[Dallas off-screen]
Let's try this differently.

No, that didn't help.

If anything, the mirrored back flip
needs even better synchronicity.

These guys were hoping to push off from
each other

to give their spins a boost of

angular momentum but being misaligned
meant only one of them felt the benefit

and tasted success.

The other just tasted gym mat.

[man] Oh.

[Dallas] Right, it's time for today's
science lesson,

that bit of the show
where we dial

down our microscopes and really examine
one particular principle and, as always,

they'll be a test so do
pay attention starting now.

What links the following?

These big kids.

[screams]

[Dallas off-screen]
This confused biker.

And this elastic
band inspector.

[man] Oh.

[Dallas] Who said
negative feedback?

No, Jones.

I'm not talking about your last report
card,

I'm talking about the property of
a system

that tries to return to its resting
state after a perturbation.

Let's take a look.

When he releases the elasticated band it
self-corrects returning to its

original dimensions.

This is a form of negative feedback as
forces act to reduce perturbations that

disrupt a system.

Balancing on the unicycle he's also
demonstrating negative feedback,

when he tips to the side

his sensory system sends signals to the
brain which coordinates

his muscles to apply force
to bring him back upright.

That last one is actually an example of
neuro mechanics

as it involves a
feedback loop

between the senses, the brain and the
muscles

but we are getting ahead of
ourselves.

So, let's start nice and simply, why is
it called negative feedback?

Maybe this guy can help
us work out the answer.

[man] Go higher!

[Dallas off-screen] Yep, it's called
negative feedback because it reduces

disruptions to a system.

The resistance band wants to return to
its equilibrium or resting state.

And it does,
rather quickly.

The spring this squirrel is pulling also
experiences negative feedback,

it wants to reduce
disruptions and correct itself.

Yeah, that's better.

Okay, question two.

Does negative feedback make
something more or less stable?

Well, I can see why you
might have guessed less.

But it's actually more.

Initially this bike and biker are
staying stable

thanks to negative
feedback.

Once he falls the bike's gyroscopic
effect

and the angle of the steering
column

help it to continue
to self-correct,

which in this case
is a bit of a shame.

[man] That's it!
Give it some, man.

[man] I'm trying to.

[Dallas off-screen] Aren't
you a bit big to be on that?

[man] Here we go.

[laughing]

[Dallas off-screen] Yes, you are and let
that be a lesson to you.

The spring of this kid's playground
bouncer

struggles to self-correct
from the

perturbation caused by the weight of a
fully grown man

but some perturbations
are just too big.

[man] Here we go.

[Dallas off-screen]
And equilibrium is restored.

Alright, last question.

What type of feedback lets people or
animals balance things or themselves?

This bird is doing a lot better
than our human researchers

and is using neuro mechanical
negative feedback

to stay on top of things.

Who's a clever boy then?

This fitness fanatic is also using the
feedback loop between his brain,

senses and muscles to stay on
top of this balance board.

Yeah, the bird
was definitely better.

[Dallas] There's an old saying that we
use when something is very, very easy.

We like to say it's
like falling off a log.

[man] Whoa.

[Dallas off-screen] The good thing about
it is that it's universal.

From mountain
streams in the caucuses

to a chilly peat-filled
moorland in Scotland.

Yep, logs are tricky.

This is Australia so at least the water
should be a bit warmer.

But there's probably something in there
that wants to eat you.

While falling off a log is simple,

it follows that staying on
one should be hard.

Well, with a little science
it can be made a lot easier,

especially if
you know your logs.

As a general rule

it's much easier to walk across a wide
log than a narrow one,

thanks to its large base of
support and lower curvature.

However, if a log is wet or covered in
moss or fungus

then it will have a lower
coefficient

of friction with his shoe, meaning his
foot will slip more readily.

[screams]

[Dallas off-screen] And if that log is
suspended across a river

it might be supported by wet rocks with
low friction of their own

and might even
roll under its own weight.

So, if you wanna stay dry

you need the widest, driest, most stable
log you can find.

Let's see how our
amateur researchers get on.

That's a nice wide log but it looks damp
so it could be a bit.

[screams]

[Dallas off-screen] Slippery.

You alright down there?

That log has a fairly low curvature
gradient,

meaning the top is reasonably
flat but

a wet log was a low coefficient of
friction and when your foot slips

it really is that easy.

Okay, this log is at a bit of an angle

but it looks dry and she's got
plenty of help

so this should be fine.

[screams]

[Dallas off-screen] Which makes
that all the more impressive.

This is a thin log with large curvature
and narrow base of support,

bound with a backpack she has a high
center of gravity

so when she places her
foot it

slips one way,
sending her the other way.

[screams]

[Dallas off-screen] And making
her packed lunch a bit soggy.

[Dallas off-screen] Ah, now this log is
resting on smooth, flat rocks.

We know he needs to be careful about it
rolling away, but does he?

[screams]

[Dallas off-screen] Well, I think that
answers that question.

Here at the Science of Stupid we are big
fans of Eddie Hall,

the first man ever
to deadlift

over 1,100 pounds, but if you wanna get
big and strong like Eddie,

you need to start
a bit more modestly.

[Dallas off-screen] Just be careful with
those dumbbells.

Then after a while you
can work up to bigger weights.

But you still need to be more careful
with those dumbbells

until eventually your shirts no longer
fit around the arms,

and you still need
to keep an eye on those dumbbells.

One of the most versatile pieces of gym
equipment is the humble dumbbell,

it's a fun thing to say but have you
ever paused to consider

the science behind them?

As our man lifts his dumbbell, he must
overcome its weight created by gravity

acting on its mass,
once in motion it has momentum

and because momentum
is velocity times mass,

the heavy dumbbell has a lot of momentum
even at a low speed.

Dumbbells have retaining bolts
that hold the weights in place,

holding the dumbbells vertically

puts more strain on the bolt and can
result in

material failure and an awkward chat
with the front desk.

Some crazy kids have made dumbbells
that weigh more than 350 pounds,

that's the equivalent
of a small upright piano

or an elephant
that weighs 350 pounds.

This one is a bit
more manageable.

But it's not
without its problems.

The dumbbell's relatively large mass

means it has a lot of momentum
even at slow

speeds, enough to break
that light anyway.

A much higher ceiling but is that the
best way to hold a dumbbell?

Hmm, no.
No, it isn't.

As he's holding the dumbbell vertically
and giving it extra momentum,

he's putting even more
stress on the retaining bolts.

Resulting in material failure
and a hefty decorating bill.

This enterprising fellow has made his
own weights using household objects,

that's one in the eye
for corporate gym big wigs.

And one in the chin for him.

This basement experimenter needs to
produce a force that's strong enough to

overcome the weights, err, well weight
but when one side slips off, that force.

Is a bit too much.

I heard that
Albert Einstein said,

"I fear the day that technology will
surpass our human interaction,

the world will have
a generation of idiots."

It turns out he
didn't say that at all

but if he saw this lot,
I'm sure he would have.

[music plays through credits]