02x07 - Roof Jumping: To Infinity and Below

[bunniefuu]

[Richard, off-screen]
It's the Science of Stupid.

Yes!

This is the Science of Stupid.

The program filled
with stupid stunts...

And smart science.

We show you erratic
experimentation,

and explain the science behind
the painful consequences.

You'll learn about
Newton's third law,

optimum trajectory
and kinetic energy.

If you mess with science,
science will mess you up.

♪ ♪

Come on down...

For the Science of Stupid .

Over the next half hour,

we'll discover what happens
when momentum meets friction,

when you miscalculate tilt,

and when you get
caught out by lift.

But first, this.

BMX's, they put
you in mind of skillful young

freestylers pulling off
stunts in urban surroundings,

it's all just so cool.

Even the tricks have cool
names, such as the tail whip.

♪ ♪

[man, off-screen] Ohh! [Bleep].

To avoid ending up
like those broken bikers,

you might want to pay
attention to this

before attempting a tail whip.

[Richard, off-screen] The combined mass
of rider and bike once in the air

follows a set trajectory
called a parabola.

To spin the bike beneath him,

he pushed off the bike to make
room for it to rotate,

but he must do this precisely
to avoid flying away

from the bike in mid-air.

♪ ♪

Now if you push
too hard your body can fly

upwards to keep the center
of mass on its parabola,

so get plenty of height, don't
push off too soon or too hard.

But what happens when you
get that wrong I wonder?

♪ ♪

[Richard, off-screen] Well, he
certainly looks the part,

but can he play the part?

No.

Not enough height
equals plenty of hurt.

Ooh, that's a big jump.

♪ ♪

No height issues here,

and that's a big jump...

[crashing sound]

And that's a big fall.

He pushes the bike down too
hard so has to go up to keep

the center of mass on
its parabola.

By the time he hits the deck,
he's traveling at 30 miles an hour.

So that's going to hurt, a lot.

Let's see if this
chap's any better.

Yes he is, that was great.
What else can you do?

Oh, I preferred the first one.

By pushing himself from the
bike too hard his legs up

and nose down, into the floor.

Will this chap remember that the center
of mass will stay on the parabola?

[man, off-screen] Ohh!

[Richard, off-screen] No.

But I have complete
faith in this young man.

Oh.

His center of mass was fine,

but if the wheel
is pointing the wrong way

when the rider lands,
he's in trouble.

♪ ♪

Yeah nice tattoo, I wonder what
hurt more, the ink on the ribs

or the cut on his head?

And that's why I wouldn't try
this at my local skate park,

and neither should he.

♪ ♪

This researcher is very brave
to try and jump the fence,

but by pushing himself
off the bike early,

they're on different parabolas.

Unfortunately the ground
didn't just break his fall,

it also broke his ankle

and that's why you
shouldn't try this at home.

Not putting your foot in a bucket,
that's okay, the bike jump thing.

As you can probably tell,

I love to go to the gym, but
I do tend to avoid certain

exercises, me and the guys have
a little rule when it comes to

one armed press ups, you either
need to go hard or go home.

I like to go home,
and where's why.

♪ ♪

A one armed press up
isn't just about strength,

you need to consider other
factors that might stop you

quite literally falling
flat on your face.

Let's start with
positioning and balance.

♪ ♪

[Richard, off-screen] By positioning his
elbow out to the side of his body,

his chest muscles take some
of the work from his arms.

To stay balanced, his center
of mass needs to stay over

the triangular bass formed
by his hand and feet.

By parting his legs wide,
he makes this triangular base wider

so it's easier for him
to keep his balance.

♪ ♪

I could quite easily show you
all that right now,

but it's this old tennis
injury you see that hurts,

best I leave it to these guys.

Hi everyone!
It's me, Kenneth again.

[Richard, off-screen]
Hi Kenneth again!

Today I'll
be doing 100 push-ups.

But with someone on my back.

Kind of scared, but...

but you gotta believe,
you gotta have faith.

[Richard, off-screen] I believe in you
Kenneth, look at those g*ns, I believe.

So, 100 one-armed
press-ups you say?

I'll keep count.

One.

Ohh!

[Richard, off-screen] Yeah,
disappointing, Kenneth, disappointing.

Nice technique, but the added
weight was all too much.

In fact, if they were
the same weight,

it would make that one-armed
push-up around

two and a quarter times harder.

[laughs]

Can you do a
one-armed push-up?

Oh yeah! No problem.

[Richard, off-screen] Well, she
certainly got the gym-wear.

I hold my beer.

[Richard, off-screen] Guess
she knows what she's doing?

Alright,
straighten up your back.

Oh! God!

[Richard, off-screen] I don't
think the back was the problem.

Oh! God!

[Richard, off-screen] Forget the back,
it was her badly positioned arm

and an angle of around 30
degrees between her legs.

To keep her center of
gravity over her base,

the angles should have
been around 45 degrees.

[man, off-screen] All right,
straighten up your back.

Oh! God!

[Richard, off-screen] Ah, this
looks more like it.

Right.

[girl, off-screen] Are you okay?

Are you okay?

[Richard, off-screen]
Why are whispering?

Her legs were
perfectly positioned,

but her arm lets her
down, very quickly.

Ouch.

For a one arm, spread
your legs apart like that.

[Richard, off-screen] Here's a clearly
fit scientist

who sounds like he knows his stuff.

Then you wanna take your elbow out
and come down.

[Richard, off-screen] But
probably not like that.

Then you wanna
take your elbow out

[Richard, off-screen] What he said was
right, what he did wasn't.

...and come down.

[Richard, off-screen] His arm was
positioned too far out to the side,

which made it difficult
for him to hold his weight.

Ohh!

[Richard, off-screen]
So he fell on his face.

This doesn't look like your
average forest pastime.

Can you guess what law this
chap is about demonstrate?

[Richard, off-screen] The law
this man is demonstrating

is the law of
conservation of momentum.

That means that
during this collision,

the momentum lost by the truck
will be gained by the man.

Because the truck is so
much heavier than the man,

he's thrown back at about twice the
speed the truck was traveling.

♪ ♪

As activities go this qualifies
as stupid and not to be copied

at home, or even in a forest.

To be a sportsman
you need to have

fitness, strength,
pace, and stamina.

But if you haven't got any of
that you could try snooker,

joking aside...
and that was a joke, just,

you may not need physical prowess to
excel at pool or snooker,

but you do need a lot of
skill to do this.

♪ ♪

But this is the
Science of Stupid ,

we're not interested
in people like that,

we're interested in
people like this.

♪ ♪

[shouts]

Everyone loves a trick shot,
especially one that involves

the ball jumping through
the air as if by magic,

but to be any good at them
you must understand the action

and reaction forces of
Newton's third law.

So listen up.

[Richard, off-screen] If you hit
a ball down into the table,

the table will exert and
equal and opposite force

onto the ball, making
it jump through the air.

And the bigger the angle
between the cue and the table,

the shorter and steeper
the jump will be.

♪ ♪

It all sounds straightforward,

but get the angle or height of
your cue wrong and you'll either

have no jump at all, or you'll
scoop it uncontrollably

and nobody wants that.

[Richard, off-screen] This
is what I like to see,

a team of scientists
hard at practice.

Smashing!

There's certainly no Newton's
third law at play from the table,

he just scoops
it right into the light.

That bright spark.

[man, off-screen]
One, two, three!

[Richard, off-screen] Researchers need
to do a lot of brave things in the name

of science, but putting your
head on a pool table is...

I don't think
that's one of them.

What did you expect?

Hit that coin...

We're going to get both ba*ls in

at the same time, alright?

-Hold them both?
-Yep.

-Just hold them.
-Keep it steady.

[Richard, off-screen] How's
he going to hit both ba*ls?

Oh, I see.

Well, he did warn you.

Although technically the cue
ball does jump after hitting

the coin, I'm putting this
one down as a mean trick.

What a difference a
few degrees can make.

In an ever more technological
world where children are more

likely to be at a screen
than in a park,

old people like me get
great pleasure in the fact

that some of history's more
basic games are still enjoyed,

and they don't come much
more basic than the Frisbee.

-[man, off-screen] Oi!
-Or so you'd think.

♪ ♪

Oh!

[woman, off-screen] Ohh!

It is just a
simple piece of plastic,

there really aren't many variables
that can make it go wrong.

Well, not enough spin I suppose,
not enough speed and I guess

you need to make sure that the
angle of attack is correct,

oh, and tilt.

I think you'd better
have some science.

♪ ♪

[Richard, off-screen] For a Frisbee to
fly successfully it must be stable,

that means spinning fast enough for
gyroscopic effect to kick in.

This means it can behave like a nice
stable wing and generate lift.

The faster the flow of
air over the Frisbee,

the greater the lift and therefore the
further it will travel.

A Frisbee must be throw
horizontally

so that that the lift
is vertical.

If it's titled there's
a sideways force

that sends the
Frisbee off-course.

♪ ♪

So to be successful you just need to
throw it hard and straight

and flat
and with plenty of spin,

and that's not even taking into account
what's going on with the wind.

How do people ever get
these things in the air?

Oh, hello. What's up?
Nice to meet you.

Frisbee. Peace.

[Richard, off-screen] I'm pretty
confidant the intended target

was that tire.

Frisbee. Peace.

[Richard, off-screen]
Because of the tilt

at the throw
the Frisbee was always

going to veer right, and
right into that window.

[glass shatters]

Say, 'Hi Grandma!'

[Richard, off-screen] Hi,
Grandma!

Ohh! [Bleep].

What did you do!?

[Richard, off-screen] He threw
a Frisbee in Mum's face.

Just then.

With no spin, there's
no gyroscopic stability,

so aiming is very hard.

Which is ironic considering
he hit his target.

Ohh!

[Richard, off-screen] This is Mel, she's
never thrown a Frisbee before,

but how hard can it be?

♪ ♪

Oh, quite hard for her, apparently.

There's a bit of spin so it's stable
enough to just about act as a wing,

but she can't control the angle of
attack, sending it towards the bin.

Rubbish.

[boy] Hello.

This is called...

the Frisbee man!

[glass breaking]

[Richard, off-screen] That was a
fast throw with lots of spin.

♪ ♪

[glass breaking]

Oh, shouldn't be
doing that indoors.

Guilty face.

♪ ♪

I don't know what
he's aiming for here.

♪ ♪

But it probably wasn't those.

He throws with good
spin and speed,

but the lift created from his
angle of attack and the wind

coming off the sea bring
it hurtling back to land

with painful consequences,
not for him...

Him.

When someone finally
gets it right though,

please don't put a
camera in the way.

♪ ♪

[man laughs]

A professional
ice skater can glide around

on the ice with all the
grace of a ballerina,

making a very difficult
sport look easy.

But amateur ice skaters, mm...
not so much.

♪ ♪

If you're traveling
at speed across ice,

you need to be able
to stop safely.

You have options, you could
either perform a hockey stop,

or crash into a barrier.

And if you don't want to hit the wall,
you might want to know this.

♪

[Richard, off-screen] A successful
hockey stop requires the skater

to dig the edges of his
skates into the ice,

creating enough
friction to stop him.

Not enough friction means
the skater won't stop,

whereas too much
means he'll fall over.

This is because the frictional force is
acting at the skaters' feet,

not at his center of mass,
therefore the frictional force

has a turning effect
called a moment,

which rotates the skater
around the skate blades.

This can be countered by the skater
leaning backwards as he stops.

The faster he wants to stop,
the more he leans to lean backwards.

Simple.

At speed that optimum blade
angle is around 45 degrees,

dig in too little
and you'll slide on,

dig in too much and
you'll have a moment.

It is quite a fine line between
success and failure and moments

are anything but magic...
moments, sorry.

[Richard, off-screen] Let's see if this
guy gets the right amount of friction.

No, he doesn't.

He doesn't dig in enough,
and not enough friction

equals bruised backside.

With this run up she'll probably need
plenty of friction to stop.

♪ ♪

Much more than that.

Because there isn't enough
friction the ice doesn't stop her,

but the barrier does.

We definitely need
more friction, people,

hopefully this chap
can provide it.

♪ ♪

Not that much.

By digging his
foot down too hard,

the moment caused by the
friction sends him flying.

♪ ♪

What a lovely night
for a skate,

if you call that skating.

Going at that speed I
assume he can stop properly.

[crashing]

No, what did we just
say about moments?

By digging his right
leg in too hard,

he's created a moment that
rotates him into a nose dive,

into the crash barrier.

He smashes into the wall with a
force equivalent to four times

his own body weight.

Ouch.

Hovercraft,
land and sea traversing vessels

that can glide over a variety of
surfaces of a cushion on air.

It might sound impossible, but
actually they are so simple

you can make them at home, but
I wouldn't bother if I were you.

♪ ♪

[man laughs]

♪ ♪

[boy] Ohh!

Whether you're piloting a homemade or
factory hovercraft

you won't get off the ground if you
don't understand the science behind it.

Or should that be
under it... behind it.

♪ ♪

[Richard, off-screen] A hovercraft works
by blowing air underneath it,

the air below the hovercraft is
a higher pressure than the air

above, creating lift.

This creates a cushion
of air held in by a skirt

for the hovercraft to float on,

which means that there is
very little friction,

and this allows it to glide
over various surfaces.

When a hovercraft is sideways
on a bend,

it presents a longer edge
to the air rushing past,

which can result in a flip.

To avoid this, a pilot
can lean out on the bend,

using their bodyweight to
try and keep the side down.

I have to say the thought
of traveling over water

on just a cushion of air
doesn't really appeal to me,

but whatever floats your boat.

Sorry, I'm...

[Richard, off-screen] Ah,
we're with the pros now,

I'm sure they'll fare better...

♪ ♪

Or worse.

♪ ♪

Bumper cars anyone?

♪ ♪

Traveling sideways on,
number 44 has even more lift

beneath his skirt.

♪ ♪

And my mom always told me
not to be lifting skirts.

♪ ♪

Here he is again
on a nice straight,

no cornering issues
ahead here surely?

[man over loudspeaker] Oh!

[Richard, off-screen] You do need to
turn early in these things,

but not that early.

Another hairpin, I'm hoping
he gets round better.

♪ ♪

Oh, flipping heck!

♪ ♪

Air under his skirt

equals head in the dirt.

What a nice sunny day for a
ride out in your hovercraft.

♪ ♪

Oh, he's found himself a
nice bit of shade there.

♪ ♪

When he hits the bump,

the increased air under his
skirt sends him spinning.

Number 99 now going all
out to win this race,

but remember don't
overdo those corners 99.

Or should that be 66.

He hits the corner at such
speed that when he goes side on

the longer edge means he
flips to the floor...

[crashing sound]

Hard.

Well, I think we've reached our pain
threshold for another week.

Einstein said the difference
between stupidity and genius

is that genius has limits,
so be a genius,

know your limits, and don't try
what you've just seen at home.

Oh!

Oh!

[boy] Oh!

[laughs]