06x17 - Ramps, Pogo Sticks and Drones

[bunniefuu]

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

Yes, this is the show where intelligence
and idiocy are combined.

As dim-witted daredevils
risk life and limb

in the pursuit of
scientific knowledge.

We'll reveal what went wrong.

And why.

With the help of some
fundamental laws of science

such as curvature.

Impact force.

And lift.

So sit back and pay attention.

It's the Science of Stupid.

In this show we'll explore...

Sideways force.

Independent trajectories.

And surface tension.

But first this.

You may think of earthquake detection as
being cutting-edge science,

but did you know, the earliest
seismograph dates

all the way back to the Han Dynasty,

when Zhang Heng built a bronze vessel

where dragons dropped ba*ls into the
mouths of toads

to alert them when there was an
earthquake.

Of course, you often don't need to be
told when there's an earthquake

as it's fairly obvious.

This is Ecuador, which is well known for
its seismic activity.

And this is China.

Worldwide, there are hundreds of
thousands

of minor earthquakes each and
every year.

Which all adds up to
a lot of tidying up.

As we all remember from school,

an earthquake is the release and
propagation of

energy from a fault
in the earth's crust.

Massively powerful and hugelydestructive
earthquakes can rock your world.

But where do they come from?

Stresses build up in the top layer of
the earth due to plate tectonics.

These are resisted by friction and
rock's inherent sheer strength,

but eventually the
pressure becomes too much.

And the rock will slip.

Energy propagates out in three
dimensions as seismic waves.

P-waves are longitudinal waves that many
animals are better at sensing than us.

S-waves are transverse waves that create
side to side,

or up and down oscillations.

And surface waves can make the ground
surface roll like the ocean.

The Richter scale is a way of measuring
the magnitude

of an earthquake based on
how much

the ground has moved, considering the
distance from the epicenter.

The largest earthquake every recorded
was in Bio Bio, Chile.

Measuring 9.5 on the Richter scale, it
created 35-foot-high tsunami waves



[man, off-screen] This
is a landslide...

...that we are climbing through.

And it looks...

...relatively fresh.

[Dallas, off-screen] The thing about
earthquakes is, once there's been one,

you're likely to
have aftershocks.

[man, off-screen]
Major earthquake.

Holy ****!

[Dallas, off-screen] As once a fault has
slipped, if there's any residual stress

then it's more likely
to slip again.

[man, off-screen] That is
some scary **** right there!

[Dallas, off-screen] But if you have
pets

you might get a heads up before the
quake hits.

These dogs react before
any visible shaking because

they're more sensitive to the
smaller, longitudinal P-waves.

This guy is desperate to
get his homework finished.

But those S-waves.

[man] Ah!

[Dallas, off-screen]
Have other ideas.

Side to side oscillations apply sheer
force to the table

and the chair he's sitting on.

Panic also makes him push it backwards

until his center of mass is beyond his
base of

support and gravity
pulls him down.

Here we learn two facts.

One, DVDs are still a thing in Taiwan,

and two, the transverse oscillations
created

by S-waves... can
cause quite a mess.

Bike ramps can be the gateway
to impressive stunt central,

but they can also be the fast track to
Painsville, population, you.

So how do you make
it a little safer?

Well, what about adding
a river into the mix?

Actually, this doesn't
look that safe.

But I'm sure it's more
harmless than it looks.

[screams].

No. Maybe this is another
one of those things...

that's best left to people
who know what they're doing.

[laughs].

People like Vittorio Brumotti,
who, back in 2009, managed

a 56-foot-high jump into
water with his bicycle.

That is about three times
the height of a giraffe,

so I assume he had a
natural flair for physics.

For our man to make a good jump, he
requires sufficient launch velocity

for a large parabolic
trajectory.

A steeply angled ramp gives a high
launch angle

for plenty of airtime for a flip.

But he must be careful

controlling the position of his center
of mass in order to

control the amount of angular
velocity that's generated.

On landing, hydrodynamic drag will slow
the bike and our man gradually

for less impact force, or
at least that's the idea.

[crying].

This seems ridiculous to me, but I am
always ready to be persuaded.

So now we're armed with
a bit of science,

it's time to put theory into
practice in the real world.

If you've watched this program for
any length of time,

then you'll know that
ponds only spell trouble.

[laughter].

See what I mean?

The undersized bike and rough terrain
limit this boy's launch velocity,

and with his center of mass so
far forward and high up,

when he hits the ramp
his front wheel slows

and his momentum sends him
into that stinky pond.

Right, full-sized
bike and grownup.

[screams].

Who should know better.

The steepness of the ramp
means that as he rides up it,

the gravity acting
downslope decelerates him,

to the point where at the top
he was more or less stationary.

And with his front wheel off the
edge, his back wheel acts

as a pivot to rotate him
into an undignified dive.

With a run-up of that distance, this
jump should have real potential.

This is a huge disappointment.

He gets plenty of momentum,
but when he hits the wet dock,

sideways force
overcomes friction,

sending him over the
ramp without his bike.

[laughter].

Okay, one last go to
try and change my mind.

[cheers].

No, this is still
ridiculous and dangerous.

[Dallas, off-screen] This
looks like a fun night out,

but what scientific principle is this
boisterous bloke about to demonstrate?

[Dallas, off-screen] Everyone loves a
little stupidity on a Saturday night,

but have you guessed what scientific
principle is about to be demonstrated?

Yeah, he's not gonna
win any prizes for that.

But if you said 'horizontal velocity',
you've won the right to feel bright.

To make it over the sign,

he needed to push off at a slight angle
to get a ground reaction

with both horizontal
and vertical components.

He had the height,

but he lacked horizontal velocity and he
paid the price.

Pogo sticks have provided a rich vein of
research

for us here at the Science of Stupid

and I'm particularly proud of the work
we've done on back-flips and landings.

But today our testers are
trying out some other tricks.

Our team leader in the pogo research
department

is successfully taking his hands

and feet on and off his stick while
maintaining a stable repeating motion.

Well, fairly stable.

Meanwhile, one of his colleagues is
investigating how the pressure of

competition impacts
performance.

[man] Oh.

[Dallas, off-screen] I'm not sure about
performance

but that's definitely an impact.

As a team, we've clearly got
some work to do, but I'm sure

it's nothing a bit of
science can't sort out.

Friction is key for keeping a pogoer's
hands and feet

attached to their pogo
stick.

Acting a single coherent unit,

they maintain a stable repeating motion
by constantly

moving the base of support
to counteract any rotations.

A trick almost always involves taking
one or two hands or feet from the stick,

so he must control his movement and land
back with all four limbs in place in

order to stay stable on the stick.

Now, it's worth remembering that if a
pogoer and his stick separate

they will follow independent
trajectories

that'll be almost impossible to join up
again.

Hopefully this injection of intellect
will inspire our investigators.

Our first trickster is
the high-hopping Heather.

Didn't go exactly as planned.

Planting her foot on the rock,

she expects to get a reaction force to
push her back towards

her pogo, but there's not enough
friction between her shoe and the rock

and gravity takes over.

Let's see how Tony the
trick-meister is getting on.

[laughter].

Yep, that's gonna
make his eyes water,

but nothing a few deep breaths
and an ice pack won't fix.

He successfully flips his leg over

and gets his feet back on the plate for
landing,

but on impact his center of mass is
slightly outside the base of support,

creating a turning effect.

Meaning the stick launches him a
significant

horizontal component to his velocity.

Which sadly takes him...

[laughs].

Onto the fence.

We're not having
much luck today.

But this looks promising.

And by promising...

I mean very painful.

Coming down with one leg hooked over the
bar, only friction between her other

foot and the plate keeps her steady on
the stick,

but that reduced friction isn't enough,

and her foot slips forwards whilst the
rest of her rotates backwards.

And that, gentle viewer,
is why you wear a helmet.

It's time for today's
science lesson.

This is the part of the
show where we take apart

one specific principle
to see how it works.

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

This terrified toddler.

This soapy street.

And this muddy ATV rider.

[laughter].

Did you guess that they were all to do
with surface tension?

If you did, well done.

But don't let it go to your head

because we've got science to learn and
then a test.

The molecules in water are attracted to
one another with hydrogen bonds,

which makes it cohesive.

It sticks together.

Where water meets the air, these
cohesive forces

create surface tension that tries to

minimize the surface area and pulls
small droplets into a spherical shape.

But soap can reduce
the surface tension,

allowing a thing film to
stretch out in a giant bubble.

Before the air pressure overcomes it and
it too splits into droplets.

Hopefully after that you
have a handle on the science,

because now it's time for
that test I promised.

Question one.

What is it that
allows me to do this?

The answer of course is surface tension
created by hydrogen bonds in the water.

But they're weak
and that cat...

is heavier than it thinks.

[laughter].

This insect on the other hand is
sufficiently lightweight

to not exert too much pressure on

the surface layer and so can be
supported on it without sinking in.

Question number two.

What does surface tension do
to a small amount of water?

It tries to reduce
surface area,

pulling the water into more
or less spherical droplets

as this cat is demonstrating with a
classic head under faucet maneuver.

The Leidenfrost effect is a physical
phenomenon that also illustrates this.

A liquid in near contact with a surface

significantly hotter than its boiling
point

produces an insulating vapor layer which
stops the liquid from boiling rapidly.

The vapor layer also creates a repulsive
force,

making the droplet hover over the
surface

rather than making
physical contact with it.

Okay, now the third
and final question.

Does soap increase or
decrease surfaces tension?

That's right, soap decreases surface
tension,

meaning thin films of water can be held

together for longer
like these bubbles.

So that ends our lesson
on surface tension.

Class dismissed.

[laughter].

[Dalas] You all know that health and
safety is one of my biggest concerns,

which is why I'm always cautious about
skateboarding

and I am doubly cautious if

you're planning to add a
flip into the equation.

If you prepare sensibly, you can avoid
unnecessary risks

and stay safe like this guy.

But if you must up the
difficulty level...

wear a helmet.

But remember, no matter how cool it
looks,

skateboarding is still very dangerous.

[cheers].

This is not a stunt for beginners, but
if you are a highly skilled skateboarder

and are considering doing a flip, it's
essential to understand the science.

For a front flip, the rider needs to
generate

angular momentum by throwing his

bodyweight forwards whilst applying a
force to the ground with his legs.

A ramp launches him into a parabolic
trajectory

with plenty of airtime so he can

tuck his legs in to
increase angular velocity.

And land carefully to dissipate his
remaining forwards momentum.

So there you have it.

Personally, I'm still not keen,

but given the choice between a
skateboarding flip

or eating my own shoe,
I'd choose the shoe.

But then I do have particularly
delicious looking shoes.

Some people's shoes however
aren't made of sandwiches.

He has time to flip perfectly,

so that his forward momentum takes him
onto a precise

landing spot near the
center of the other board.

But he hits the second board slightly
off center

creating a turning effect that allows
his

momentum to throw him...

forwards.

This guy appears to
favor a long run-up.

I'm not quite sure what flip he's
intending to do,

but at least he's got a good crowd.

[cheers].

Which is gonna make it tricky
to deny that ever happened.

His long run-up allowed him to build
speed for a high launch velocity,

but the ramp he took off from

didn't offer a launch angle that was
sufficiently steep

for a more vertical
trajectory.

So as he leaned forward and
tucked for his rotation,

his trajectory intersected
with that fence.

Hopefully third
time's the charm.

[man] Ugh.

[Dallas, off-screen] Less
charm, more harm.

He uses the ramp to help throw his
weight backwards for a back-flip.

As he lands and bends his knees to
absorb his downward momentum,

his foot clips the edge of the board

creating a turning effect that rotates
it up,

in quite a painful way.

In recent times drones have
become incredibly popular.

No longer the preserve of the military,
now anyone can fly one.

But when you finish flying how do you
get that out of the sky?

These guys have made
it look remarkably easy,

probably because they've
had lots of practice.

But a little less
know-how could be...

costly and painful.

Yep, catching a drone can be
surprisingly hard

and unexpectedly dangerous,

and that's because the four propellers
of a drone spin at more than


minute, which is pretty fast.

In order to hold a drone safely and
securely,

our man should grip a rigid and

non-moving part from beneath.

Either the body or the legs
present good surfaces to grasp.

But he must remember that the propeller
blades

have high angular velocity which gives

their tips a lot of kinetic energy.

This, coupled with the sharp edges of
the air foils,

means that the very high pressure

can be applied to
and break the skin.

So to avoid injury, low relative speed

with allow our man to grab the drone in

a safe place and avoid finding out why
they're called rotor 'blades'.

Personally, I prefer to keep my distance
from drones

and my advice to you would be to

avoid catching
one at all costs.

Unfortunately, not everyone
has my good judgement.

Okay, that does look alright,

but that drone is quite a long way away
from him now.

But don't panic, just hit
the 'return to home' button.

What a useful feature that is.

This is a fairly large drone

with some pretty serious propellers
spinning at high

angular velocity, so the tips could be
moving at around 100 miles an hour

and have a lot of
kinetic energy.

Great for getting it safely
back to wear it wants to go.

Less great if
you're in its path.

[man, off-screen] Yup, that's
what happens when drones attack.

[Dallas, off-screen] This is
exactly the sort of situation

where catching a drone
is really stupid.

[man, off-screen] Ready?

[Dallas, off-screen] A moving boat is
definitely

going to up the difficulty level
of this dodgy procedure.

[man, off-screen] Don't be shy.

[Dallas, off-screen] But he
does seem pretty confident.

[man] Keep going, keep going

[Dallas, off-screen] And by
that I mean overconfident.

On a moving boat it's hard to get a low
relative velocity

between drone and catcher.

The pilot doesn't manage and instead of
his hands grabbing the body,

they hit the propellers.

And since they have a high angular
velocity,

their tips have a lot of kinetic energy

that must be dissipated on...

[man] Argh.

[Dallas, off-screen] Impact
with his fingers.

[laughter].

[Dallas, off-screen] Back on dry land,
that should make this a bit easier.

Nice catch.

Terrible throw.

Why on earth did you do that?

[man] It hit me!

[Dallas, off-screen] Typical.

While this guy makes a heroic catch, his
friend speeds the blades up.

One hits his arm and the kinetic energy
is transferred in quite a painful way.

[man] It hit me!

[Dalas] After all that,
I'm left with these words

from Stephen Hawking
ringing in my ears.

"Life would be tragic
if it weren't funny."

[music plays through credits].