Hi all, I'm Diana.
Last week I made a video with five of my favorite physics
tricks and promised that I would share
the physics of those this week, which I will deliver.
But what you didn't see in that video
is that when you hear about these demos,
they sound so simple and so easy to set up,
but that was not our experience when we tried these out
for the first time.
So if you only want the demos with simple directions,
a link to the shorter version is in the description.
So you can either try them yourself,
or if you've seen them before, try them
with the young people in your life.
But if you want all the physics, stay
tuned for this video with my friend Jabril.
Here goes.
This episode is supported by Prudential.
Do you think I can balance two forks
on the edge of this match on the edge of this glass?
No.
Really?
I'm staying firm on this one.
All right.
Hm taking some cheats, huh?
Well, that doesn't work.
OK, I've never tried it before.
Is this like the balancing bird?
I think that's the idea.
No way
Woo!
No way.
DIANA (VOICEOVER): So the forks balance
because the center of mass, or the average of where
all the mass is on the fork sculpture,
is in a particular place.
Objects topple over more easily if their center of mass
is above and off center of the balance point.
In our case, the forks hang down below the edge
of the glass and forward a bit, so they're balanced.
It's hard for an object whose center of mass
is already lower than the balance point
to fall over the balance point.
That was awesome.
Second experiment-- pour some water onto that plate, please.
All right.
OK, we're going to put a match.
Now cover it.
Nice.
Oh, wait.
Did you see what happened?
I seen what happened.
The real question is, do I comprehend what happened?
That's mad.
That's cool.
OK, do you want to describe what you're seeing.
It's raising--
The water level?
Yeah.
What else is produced when you burn a match?
We got CO2.
We got heat.
Heat.
Yeah, heat is produced.
So the heat from the flame speeds up the air molecules
so they move around a lot more, and the air expands.
As soon as you cover the flame, there's
not enough oxygen for the match to keep burning,
so it goes out.
And the air will immediately start
to cool down, contracting as it does and taking up less space.
This creates a lower pressure inside than outside the glass,
which forces the water up.
But that's not the whole story.
When you burn wood, you produce some water vapor.
What's being converted from to make water?
Wood is largely made of cellulose.
Combine that with oxygen, and you get CO2 and H20.
Now, once the flame goes out, the water vapor
hits the sides of the glass and cools
and some will condense into liquid form.
Liquid water is 1,600 times more dense
than water vapor, and this contributes
to the low pressure,
But there are other reactions taking
place that can affect the volume of gas before and after.
And it's possible some of the CO2
can get absorbed into the water.
So overall, it's not a simple process.
I see.
Yeah.
Diana, that was crazy.
But third experiment.
All right.
OK.
Ta-da.
They're supposed to do something else.
Oh, that one flipped.
That's pretty amazing.
This is a great party trick.
My favorite party.
You can show all your friends.
DIANA (VOICEOVER): At this point,
we added some tap water to the carbonated water
to dilute the amount of dissolved carbon dioxide.
OK, so they sink.
Oh, yeah.
Some of them sink.
Oh, yeah.
And it's coming back up.
Oh, there goes another.
Oh, there we go.
Now, I wonder if any of them will go back down.
Oh, so we are expecting to float-- or to sink again.
Oh, I gave that away.
Yeah, so I think that we probably need.
Oh.
Oh, no.
What?
Down it goes.
That is awesome.
That is so awesome.
I'm really glad you think it's cool, because this
is like 20 minutes later.
Up top.
That's really cool.
Why do you think the peanuts rise up?
In normal water, they sink.
And obviously, like, some of them are sinking right now.
But then what's happening on them?
Oh.
The bubbles help them float to the top,
and the bubbles eventually pop, and they sink.
Yes.
Is that really what's going on?
Yes
That's incredible.
That's exactly what's going on.
DIANA (VOICEOVER): So there's carbon dioxide
dissolved in sparkling water.
Once you open the cap, and the pressure's released,
CO2 gas bubbles start forming.
But they can't form everywhere.
They need a nucleation site, a place like the rough surface
of salted peanuts.
Some champagne glasses have scratches etched in,
so when the glass is clean, the scratch
becomes a nucleation site for the bubbles
to form, creating perfect bubble lines.
It's, like, essentially generating
like a raft on the peanuts.
Number four.
Go ahead and light it.
Ready?
Yes.
Dang it.
That was interesting.
It was interesting.
No.
Folded the paper towel, and we're
going to put a couple more matches.
Wow, wow, whoa.
[INAUDIBLE]
Oh.
OK, plastic wrap did not work.
But we put some olive oil around here,
trying to make this seal better.
Coming in hot.
[INTERPOSING VOICES]
It lifts.
Yeah!
It lifts.
That is awesome.
So I was like, we're going to have to nix this one.
What do you think is happening here, Jabril?
All right, so it's creating that suction from the process.
Why it brings the plate along though--
because that's closest hard surface?
It's basically what's in the way.
DIANA (VOICEOVER): Just as with the water rising trick,
the air inside ends up at a lower pressure,
but the plate is blocking the opening, so it stays low.
Now, the atmosphere always pushes
with a constant pressure, even below a plate.
So once the suction starts the air
is pushing harder upward on the plate than the air on top
is pushing downward.
So the plate can move up with the glass.
Number five.
All right, for this experiment, I'm
going to put a stick through a balloon.
You're going to pop a balloon.
You think it'll pop?
It's going to pop.
Even if it doesn't pop, I still feel like-- wow.
How do you feel about that, Jabril?
Indifferent.
Indifferent?
I feel very indifferent.
What?
I just poked a stick through this balloon.
Do you think I could put it all the way through?
No.
I've never done this before.
I have never--
Are you serious
--done this before.
For a first try, I'm very impressed.
I know.
Check that out.
I'm very impressed.
You want to try?
OK.
Jabril, it's all you.
All right, any tips?
Yeah, this tip.
Diana, it didn't work.
Oh, so you're putting it through the bottom, huh?
I am.
Yeah, why?
I believe that you went for the thicker part.
OK, so yeah-- this little nubbin, the tip of the balloon,
is a bit thicker.
Like, the rubber's a bit thicker.
So it's less likely to break and then become, like,
a catastrophic rupture.
And then over here, you've got all this rubber
coming together.
And so it doesn't get stretched as much.
So therefore, it ends up being thicker,
despite the fact that this part is not made of thicker rubber.
Right, right.
You can stick a balloon without popping it.
Or with popping it.
Thanks for helping me with all these experiments, Jabril.
Thanks for having me.
Thanks for blowing my mind.
I know how to be the cool guy at parties now.
Thank you guys for watching, and as always--
BOTH: Happy physics-ing.
Hey, last thing.
Jabil has a cool channel called SEFD Science.
The link is in the description, so you can check that out.
And also, if you've got a more creative way
of making these demos work better
or of testing something different about the phenomena,
let me know in the comments.
This episode was supported by Prudential.
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[MUSIC PLAYING]
Diana out.