Hey, it's Diana, and you're watching Physics Girl, back with video 2 of Riddles with Legendary Music Producer, Kurt Hugo Schneider.

This is one of my favorite series, because I found people that like riddles almost as much as I do and who think I'm nice enough to make them look good on camera attempting the riddles.

So that's where we left off yesterday, with Kurt thinking about the answer to the bowl riddle, which went like this.

A crazy chess master has put all of Kurt's instruments in a closet with a bomb, and the bomb is gonna go off in 30 minutes unless we can get the floating ball to the bottom of the bowl.

Basically, how can you get the ball down, so it's touching the bottom of the bowl, but without touching the ball?

But, there are a few riddles-- rules, ugh, I meant rules, which I mostly came up with after the fact because Kurt tried to find every possible way to work around the spirit of the riddle.

Let's see.

Can I boil the water?

Can I just like put it on my stove?

DIANA: You have to keep the water in the bowl.

KURT: I see.

I just can't attach some-- like, get some chewing gum and attach a little weight?

OK. You can't push-- directly push or directly pull the ball.

I can't do that?

You're trying real hard to work around my riddles.

I am.

Were you a really good, but lazy student?

Um, I was definitely a lazy student, yeah.

DIANA: I got it.

OK, well, let me think.

I can't just scoop it up in a little cup and put it there?

But I don't fully understand what you mean.

So imagine I'd like-- Can you show me with a cup.

I'd just scoop a real, like, could I?

I don't know if this is cheating, but if I basically just get that, and then just put it in the bottom.

Bam!

Now they touch.

DIANA: Oh!

I see what you're saying.

Bam!

Look at that.

That's touching.

You can't see the inside of this, but I guarantee that ball is touching.

No, that's not-- that's cheating?

Or is that valid?

You know what?

I'm gonna allow that.

Oh!

OK, OK.

I'll give you a high-five for that.

But I feel like-- Is there a simpler solution that I'm not getting?

There is.

OK.

There is.

And also, I feel like if I added another rule, which I didn't-- I just need to have like a ton of rules for you.

Ugh, the rule that I should have created at this point is simply, you cannot touch the ball, even with another object.

You cannot touch or alter the ball in any way.

So now see if you can get the riddle with that rule.

Pause if you want to leave a guess in the comments.

Video will resume in 3, 2, 1.

Well, I mean obviously if I just put this on top, then the water goes out to the sides, and the air, I guess, just sort of pushes down and-- Yeah.

And if, I mean, it's on the bottom.

Yeah.

Whoa, that's-- yeah, I mean, obviously I have like this cup's worth of air, so I push it down-- DIANA: Exactly.

KURT: And that's pushing it down.

DIANA: Yeah!

And there's, like-- there's a little-- That's cool.

You know, that's super cool.

Er!

What Kurt is getting excited about is why the ball goes down even when you're not pushing on it directly.

When you push the cup down, the water level beneath the cup goes down, because the air trapped in the cup can't escape.

Water is pushing the air to go up, but the cup is in the way.

So all the air stays in there, and then the water level goes down and brings the ball with it.

I guess I would have thought, like, the air would compress or something, but the water pressure's not enough.

Yeah, Kurt's right.

The air does compress a tiny amount, because the pressure at the bottom of the cup gets bigger as you lower the cup deeper into the water.

But you have to lower the cup to the depth of like a three-story building in order to get the air in the cup to compress to like half its size.

I think this was a really cool riddle.

But, moving on to the next one.

Kurt?

Yes?

In what situation can two sounds make silence?

La, la, la!

If you wanna guess the answer to this riddle before Kurt gets it way too fast, then pause the video now.

We're gonna continue the video in 3, 2, 1.

Um, well, they could cancel each other out, I guess.

If they were completely phase inverted, then the waves would cancel.

That was way too easy for you.

OK.

I mean, I record all the time.

Oh, by the way, what he meant by phase inverted was that if you take two waves with the same amplitude and same wavelength, but that are exactly out of phase with each other, then they will cancel each other out when you add or overlap them.

OK, if you have phase problems in audio, it can be a really big issue.

In fact, actually, if you're just recording something like a guitar-- Yeah.

- -and a lot of people would record a guitar with two mics, maybe, because you might want to make it a bit of a stereo field, so you might have one mic that's, you know, here and one mic that sits more at the body.

You can have phase problems if you don't position the mic correctly.

In any case, I feel like this is kind of cheating, because like audio people might already be familiar with this phenomena.

Interesting stuff.

Last riddle.

OK, so I'm going to balance this broom on my finger so that it is-- Balanced?

Yeah.

So that my finger is underneath the center of gravity.

OK, so I'm going to pretend that we're gonna cut the broom right here.

Right where you balance it.

Right where I balanced it.

So now you have two pieces of this broom.

OK.

This handle part and then the sweepy part.

OK.

Which of these sides is heavier, or are they the same weight?

Uh, we've run out of time on this YouTube video, so we're going to have to come back tomorrow with the answer to this riddle.

If you think you know the answer to the riddle, put your guess in the comments, and then come back tomorrow for the video with the answer.

I will put a link to that video in the description once it's up.

I've been Diana.

You've been watching.

Thanks for doing that.

Happy physics-ing!