07x18 - Motocross, Tables and Fluid Jets

[bunniefuu]

This is the Science of Stupid.

Yes, this is the show

that extracts science from stupidity.

Watch as grown men and women...

fool around with the laws of physics...

and suffer the consequences.

We'll reveal what went wrong and why...

with the help of scientific principles
such as...

leverage...

Oh!

...the angle of repose...

...and that old favorite kinetic friction.

Do learn but don't copy.

Watch out, it's the Science of Stupid.

In this episode we'll be studying

how to control fluid jets

and how not to.

Mammalian mental prowess,
or lack thereof,

and the elastic potential energy
stored in a scorpion pose...

but first this.

If you've ever straddled 50 horsepower

of mud-churning dirt bike
at 50 miles an hour

around a motocross track

you'll know it's a guarantee
for thrills and spills.

But mainly spills.

You see, in the sport of motocross

not only are you battling the terrain,

but you can be doing so
shoulder-to-shoulder

with 40 other riders,

so why do people do it?

Well, I can only assume

it's to gather empirical data
on suspension damping,

the transfer of momentum
and centrifugal force.

A dirt bike's suspension
dissipates much of the energy

from impacts experienced on rough ground,

but those bumps and ruts can still provide

unwanted horizontal momentum,

which can easily be transferred
to nearby riders.

On corners, riders tend to converge
along similar lines

and lean to counteract the centrifugal
force pulling them outwards

and for transfer of momentum,
that's party time.

Surprisingly motocross
has been around for over 100 years,

originally on rigid bikes
with no suspension.

One can only imagine
the magnitude of impact force

absorbed by buttocks back then,

luckily today
that's largely taken care of by the bike.

Just look how those front forks
dissipate impact force as they...

Watch out!

I think someone transferred
a little bit of momentum there.

Ah, yes. He's had some momentum
transferred to him,

his bike then transfers momentum
to this bike,

and, yep, well, everyone's got a bit.

Well, I think that's about it
for transferring momentum.

- Oh!
- Almost.

I think we should move onto cornering.

The key is to pick a line
and stick with it.

These two are on the most
direct line through the bends,

but that's not always the best line.

Remember, on those corners, riders lean
to counteract centrifugal force,

bringing them closer to each other,

so they're more likely...

to do that.

So, it can be best to pick a line

that steers clear of other riders
and their wayward momentum,

and that means looking
where you're going.

Fortunately our man
was able to reduce his velocity,

so didn't transfer too much
of his own momentum.

And our fallen rider was okay,

but still a very uncomfortable place
to park a bike.

Humankind has made life
far too complicated,

other animals simply don't have to worry
about problems

like how to fill out a tax form,

remembering all 500 Internet passwords

or successfully pairing up
a Bluetooth toothbrush,

nevertheless they can still be
surprisingly adept at solving problems.

Tarquin here can get nuts out of a tube,

nuts out of a bucket...

and nuts out of a locked box.

Bravo.

But with that fibrous diet

you'd think this wouldn't be
so much of a problem.

A bit awkward.

So why are some animals
better than others at solving problems?

Some research has suggested
that in mammals

this ability is linked
to a larger brain size

relative to body mass,

it's theoretical and contentious
but no less revealing.

So, let's dig a little further
into our mysterious mammalian minds.

In a mammal's brain the prefrontal cortex

is the region associated
with complex cognitive behavior,

including problem solving.

It's believed to help the brain
anticipate future events

that will occur as a result
of each action,

which is how we approach problems.

Mammals with a higher brain size
to body mass ratio,

like humans at one to 50,

seem to be adept
at solving complex problems,

whereas further down the scale,

the hippopotamus
with a brain to body mass ratio

of about one to 2,800

tends to have fewer and simpler problems.

Another idea
called the social brain hypothesis

proposes that in primates

larger brains evolved to deal
with the challenges of a social group,

meaning that by and large group animals
would be brainier than loners,

but let's start by looking
at those brain to body mass ratios.

Hey, buddy, look.

Whilst we have
that one to 50 ratio,

horse's brains are around
a 600th of their average mass,

so as per the theory
should be relatively daft,

but when snacks are on offer...

old Harry's little prefrontal cortex
is in overdrive.

Good boy!

Dogs like Leroy here,
descend from pack animals,

and can work cooperatively
towards a shared goal.

Dogs also have an impressive
one to 125 brain to body mass ratio.

Is that all you were using Leroy for?

So, one sniff
that baby ain't gonna share...

Whoa.

...you're on your own kid.

But as I've said, that brain ratio thing,
eh, still just an idea.

Birds don't even have
a prefrontal cortex,

but parrots like Polly here
can still be excellent problem solvers.

All lights on.

Okay.

Another part of her brain,
the nidopallium,

is the avian equivalent
of the prefrontal cortex.

Do you want fresh water?

I'm fine, thanks.

But, alas, no matter what the species,

some individuals just let the side down.

My God.

Sniffles is no genius,
but, boy, he can tap dance.

A mysterious leak in the garage loft,

but can you guess what science
we're about to see?

Did you guess the science
this leaky roof would lead to?

It's a tricky one to work out in the dark.

Ah, that's better.

Yes, it's flexural strength.

His weight was initially supported
by sturdy roof beams

which have a high flexural strength,

but he then stepped off them...

and made that hole

because the force of his weight

exceeded the much lower flexural strength
of the plaster ceiling.

Still, it'll take his mind off the leak.

I'm fine! I'm fine!

Every professional baseball
player needs to start somewhere

and what better way than T-ball?

A simpler version
of baseball with a giant tee,

perfect for little learners
like this chap.

And if he's this good now
imagine what he'd be like

with a little more practice.

I mean, a-a lot more practice.

Right, for the avoidance
of broken windows and/or parents,

let's take a scientific look at that bat,

or rather speed multiplying lever.

She starts with the bat held far back
for a wide swing arc

of more than 180 degrees.

This bat's greater mass at one end
builds lots of momentum

and its length means that end

can travel over three times further
than the batter's hand.

This makes it
a speed multiplying lever

maximizing velocity to transfer
even more momentum to the ball.

Then over to the ball's
horizontal and vertical velocity,

along with gravity,
to determine its parabolic trajectory.

In 1921, New York Yankee's batter,
Babe Ruth,

smashed a record-breaking


almost twice the length
of the Statue of Liberty.

Now, I haven't checked.

But despite the name
I don't think he was actually a baby.

That bat is about as long
as he is tall, and it's heavy,

so as the lever increases the speed

angular momentum reaches proportions
that would trouble any toddler.

That's better, but now the ball's too big.

And bouncy.

Nice 180 degrees-plus swing
optimizing speed and power

but your parabolic trajectory was altered

by the proximity of the fence.

I.e. you're facing the wrong way.

Now is it Railey or Casey
who understands parabolic trajectory?

Railey, don't hit it,
let Casey do it.

Oh, it must be Casey.

Ooh.

No, maybe it was Railey.

A bit heavy
on the horizontal velocity there, Case.

Right in the face!

But, kids, even if
you have mastered levers,

momentum and parabolic trajectory...

always try and listen to your parents.

Keep your eye on the ball.

But...

No, I mean,
watch the ball while you're swinging.

...just don't take them
so literally.

Oh, poor thing.

Good job!

And now for your science lesson

where we prize apart
a particular scientific principle,

but can you guess
what it is from the following?

A test run of an exciting new motor
vehicular invention.

We'll all be driving those next year.

Are you ready?

An enjoyable chemistry
experiment.

Well, enjoyable for us.

And a street party

in need of a more
comprehensive risk assessment.

Oh, sore heads in the morning.

Fun times.

Yes, today we're looking at fluid jets.

These jets of gas or liquid
can be described as coherent

if they're ordered and consistent

or incoherent if they're
spraying all over the place.

Today we're focusing
on the behavior of coherent fluid jets.

Science, please.

As she applies more pressure

the jet builds sufficient velocity

and thus becomes coherent.

A larger aperture increases
a fluid jet's flow rate,

meaning more fluid
is passed through the hole

per unit of time.

The greater the flow rate and velocity

the more force the jet imparts.

Okay, that's your science.

How about a little test?

Question one, how does velocity
effect a jet's coherence?

- Like that.
- Oh, my God.

The expanding bubbles
of carbon dioxide in fizz

create a pressure of around


resulting in a high velocity jet.

So here it's fast and fairly coherent

but as pressure drops and the jet slows

it becomes less coherent,

just like I become after I've had
a couple of glasses of bubbly.

Question two, how can you
increase the flow rate of a jet?

Well, as luck would have it...

Over in Germany
a man is probing this very question

by tapping a beer barrel.

Currently there is a small aperture

and the flow rate remains relatively low,

relative that is...

...to now.

Yes, bigger hole
greater flow rate, wetter pants.

Question three, two factors increase
the force imparted by a fluid jet.

One factor is flow rate,
but can you remember the other?

Well, there's only one place to find out.

Space academy,
where recruits abide by strict rules.

Right, guys,
you should be sat down!

And you shouldn't be talking.

Yeah, that's them.

Whenever you're ready.

Three, two, one.

- Ohh!
- Oh, dear.

So, the second factor
effecting force is velocity.

Ejecting the water jet at high velocity
takes a lot of force,

and an equal but opposite force
is imparted to the rocket,

the rocket launches,
the rocket imparts a large force on face.

Please don't try this yourself.

Academy dismissed.

Recent evidence suggests
that our primate ancestors

were masters at leaping from tree to tree,

there are less trees
to practice on these days,

but some enterprising young jumpers

have come up with the brilliant idea
of using tables.

- Oh-oh.
- Ohh!

Actually, I've changed my mind.

It's a silly and dangerous idea

and here's the science to show why.

Most tables are sturdy enough
for serving dinner

but may not have a high enough
material strength to support his mass

and the rapid deceleration
caused by the landing.

Worst still, jumping onto an area
away from the support

means it acts like a lever
and requires less force to break.

And even a strong surface
may not offer his feet enough friction

to counteract any excess
sideways momentum,

in which case he'll slip.

If the combined physics problems

presented by
insufficient material strength,

leverage and low friction
doesn't dissuade you,

hold fire
because this next lot probably will.

Melvin here is psyching up
to apply force to that table.

Why?

To show unequivocally
that a man's mass, let's say 170 pounds,

plus the rapid deceleration of the landing

is too much for its material strength.

So, the table is broken and...

...so is Melvin.

Next test.

A park picnic table
with an overhanging edge.

So will this be a lever problem?

Nope, it's friction.

The forward momentum of his jump

easily overcomes the low friction surface
of the smooth plastic table.

Right, have you got the science
or would you like another example?

Another one.

Okay.

Hold it.

Spot any problematic science here?

Well, let's find out.

And there's your answer.

Large force applied to edge of table
creates a lever.

Legs buckle, thanks to
insufficient material strength

and as for friction,
well, did you spot the wheels?

They offer rolling resistance,
which is usually much lower than friction,

so material strength, friction, levers,

it's quite the master class.

Question, what do you get
when you cross...

these ladies...

with this chap?

Answer.

It's this.

The amazing cheerleading scorpion pose.

I told you it was amazing.

The scorpion is one of
the more challenging flexibility poses

in a cheerleader's repertoire,

it relies heavily on our ROM,
or range of motion,

and also our muscles'
viscoelastic properties,

elastic meaning they'll spring back
to shape when stretched

and viscose meaning
the longer the stretch is held

the less it'll spring back.

Science, please.

Moving into position
engages the abdominals, quads,

hip flexors and chest muscles.

These stretch like springs
storing elastic potential energy.

She's now balanced precariously
over a tiny base of support

at the limit of her range of motion,

so releases carefully
because as the muscles are released

elastic potential energy
is converted into kinetic energy

accelerating the foot outwards.

Even if you get the physics
you should never attempt

to force your body into a scorpion
without adequate training,

because the less flexible you are,

the more elastic potential energy
your muscles store.

And the more kinetic energy...

Oh, my God.

...they release.

Her chest and stomach muscles
stored so much elastic potential energy

she just couldn't hold back
the kinetic energy released.

Oh, my God.

Oh, no walls to smash into here.

Just the ground.

You see, even with
her excellent ROM,

if you lose balance
on that tiny base of support

there's not a lot of wiggle room.

Okay, how about someone
even more flexible?

Yes, you.

Go on, don't be shy.

See, now that is a very good
range of motion in those joints,

not to mention a gently elongated
musculotendinous unit.

You get an A plus.

Actually, I better
downgrade that to a B minus.

Einstein once said,
"Wisdom is not a product of schooling

but of the lifelong attempt
to acquire it."

Some of us have a long way to go.

Oh!

Ooh.

Oh, you poor thing.