*dubstep music plays*
This is 'Learning with Leland'!
In today's episode we'll be exploring some of the funky physics of non-Newtonian fluids.
Now, I know what you're thinking. You're thinking--
Leland, I'm not entirely sure what a Newtonian fluid is..is this video really right for me?
Worry not, dear viewer. In no time you'll be an expert as well on all fluids--Newtonian and otherwise.
From our everyday experience, we're all familiar that different fluids have different properties.
Some fluids, like water,
are very thin and
flow very easily.
Some fluids, like honey, are extremely thick, resistant to flow,
And....delicious!
Now the technical word for how thick a fluid is, how much force it takes to get it to shear is called viscosity.
We say that thin fluids like our water here has a small viscosity, a low viscosity.
Meanwhile, our thick, resistant-to-flow honey has a large viscosity, a high viscosity.
The technical word for fluids that taste good...is still delicious.
So, all of this hubbub about what makes a fluid, Newtonian or non-Newtonian
comes down to what a fluid's viscosity depends on,
I'm sure you've had the experience where you have ketchup in bottle and
Initially the ketchup can be very difficult to get out of the bottle.
Before it's started to flow there's not very much shear and it can be totally stuck.
But, once you introduce some shear, it can really start flowing.
That property of the ketchup's viscosity getting smaller once there's shear introduced
means that the ketchup is a shear-thinning non-Newtonian fluid.
Could you pass the shear-thinning non-Newtonian fluid?
Yeah, sure man.
Thanks.
For the opposite effect of a shear-thickening non-Newtonian fluid,
we can actually create one using ingredients available in most kitchens.
First, we start with some corn starch.
Add some water, and then we will stir it up!
This shear-thickening non-Newtonian fluid is sometimes referred to as ooblek.
Might be able to see that as I pour it slowly,
It looks very runny,
It has a small viscosity.
But as we try and move it quickly, you can see it thicken up before your eyes.
It's non-Newtonian and shear-thickening character imbues ooblek with the ability...to dance
What do we need before any experiment?
Our personal protective equipment!
This is to protect my head from any overzealous ooblek.
And this..will help me handle the funk.
Proceed by pouring a little bit of our ooblek mixture into the speaker
*music*
What's the last thing we need for dancing?
MUSIC!
Drop the beat.
*Laughter offstage*
Whoah!
Get the ooblek!
So, what we see here is the ooblek is kind of growing some little tendrils.
We have a shear that is changing in time as the speaker cone oscillates to make the sound wave,
and also in space--different positions of the ooblek are experiencing different amounts of oscillation.
So, depending on how much shear is at a given point in the ooblek in space and in time,
It will thicken correspondingly and we see this interesting behavior.
Ah, fantastic!
It danced like a fiend when subjected to the oscillations of our dubstep bass beat.
So, what did we learn today?
We learned that viscosity is a measure of a fluid's thickness.
We learned that non-Newtonian fluids have the special property that their viscosity changes
as we apply a shearing force.
And finally, we learned that if you're going to go dancing...
It's best to leave Sir Isaac Newton at home.
Thanks for watching.