Can you solve the magnet riddle? ft YouTube CEO Susan Wojcicki


Hey! I’m Dianna. You’re watching “Physics Girl,” and you’re about to see me challenge the CEO of YouTube with some physics riddles. Since we were at YouTube headquarters filming some stuff for International Day of the Girl, she very graciously agreed to answer some riddles. I will make it clear where you can pause and think about the riddles for yourself. You should. I made Susan do it. I am here at YouTube headquarters with Susan Wojcicki. Did I say it right? Yeah, you said it right. Nailed it. Susan is the CEO of YouTube, but I am roping her in for some riddles. So I heard you roped my sister in.

DIANNA: I did. I got your sister on the show. SUSAN: Yes, and so since she did it, I thought maybe I should do it. Do you have a little competitiveness there? Is there a little bit of sister rivalry? Just a little bit. Just a little bit. I just want to sneak a couple of quick questions for my audience. And a lot of them are students. A lot of them are studying. So I look up to you. I look up to– Oh, thank you. You know, I have my role models that I look up to. I’m curious who you go to for help or who you’ve gone to in the past. Well, it depends, I guess, on what area of help I need. Like, if I look throughout my career and, like, throughout my life, it would probably be my parents. I know that sounds kind of cheesy, but it would be my parents. I think it’s all of us. Yeah. A lot of us go to our parents, right? Or someone who acts like a parent for us. I can also say, while we’re here, actually my childhood idol– in many ways, she’s still really, I mean, I think an incredible woman in every way– was Marie Curie. Since I’m on “Physics Girl” channel right now, I get to mention that.

She was an incredible scientist. She won Nobel prizes in different fields. Her daughter won a Nobel Prize. And so I always just thought she was a really inspirational person. But I couldn’t go to her for advice. I had to go to my mom and my dad– Unfortunately. Like everybody else. OK. Let’s do the riddles. OK. SUSAN: OK. Are you ready for this? Yeah, I am. Woo-hoo. All right here’s the first riddle. I have a prop for it. I’ve got a little tissue here in the neck of this bottle. How can we get the tissue out without touching it? Basically, you can’t touch it with your hands or a tool. No tools. Can I just check this out for a moment? Yes, you can. I guess I’ll look and see what’s going on. Well, I could just like turn it over and go like this. There! See? There! It worked. Physics. Gravity, it pulled it out. Outsmarted by the CEO of YouTube. SUSAN: OK. I’m going to do it again. OK, so no turning it upside down. Can I pour water in and then just have it float up? Oh, interesting. Well, I could pour water in it, and then pour the water out. Yeah, but then you’d need to– Turn it over. So if it were light, like if it were, like, a little plastic ball, it would definitely come out. But this is a– This is questionable. This is a– A surefire way to do it right here and now. Well, you have water right there. Right here.

I feel like you’re cheating, but also it’s more like outsmarting the riddle. [DING] It’s just a plain bottle. And there is just a– [BLOWING] Oh, hold on, it went the opposite direction. [BLOWING] There we go. Awesome! Yes! There we go. Yeah. It’s out. You got it out. OK, so why did you think of blowing in it? Well, it’s like, well, what else was I supposed to do with it? Yeah, but it was weird that it started to go– like, I thought it would go in. Yeah. And somehow, it went out. I don’t know why. Yeah. Can you explain that to me? I would love to explain that to you. Like, if you’re blowing air in there, some has to come out. You’re blowing air into the bottle, but there’s already a lot of air in there. So that gets pushed out, forming a messy sort of U-turn shaped stream of air. The tissue gets caught up in that and flies out. But the tissue doesn’t get that far in the bottle and then circle back out because most of the airflow happens close to the mouth of the bottle because it’s like a crowded room in there. Imagine even more people trying to push in through the door. People close to the exit will get pushed out. But you probably won’t affect the people far in the room too much. So while the tissue might get initially pushed in a little bit, it’ll get pushed right back out. Wow, that was very interesting. That was great. Yeah. OK, good. The pound around. Yes. It really surprised me. It went the opposite direction than I expected. Riddle number two. Are you ready? Yeah, maybe. These are batteries, but we’re going to use our imagination and pretend that they are two iron bars, both are identical. One of them is magnetic. One of them is not. They are the same weight, the same size. You go into a room to figure out which one of them is magnetic. So one of them is iron, and one of them is magnetic? Well, they’re both iron, but one of them is magnetized. OK. So they so they look identical. They have the same feel, same touch, same weight, same density, everything. You go into this room, you don’t have anything else metal that you can try sticking them to. And you have to figure out which one is the magnet. OK. So if one was magnetic, it would go [PWICK],, right? Yeah. But they would stick to each other. And so I wouldn’t necessarily know.

DIANNA: Yeah. You wouldn’t know which one is actually causing the force. Exactly. This is a trickier one than the bottle. This is the kind that people like thinking about for a while. This is the one I’m sure my dad would be able to figure out. Your dad would like this one? Well, I’m sure he would figure it out because I have to think that has to do with some properties of magnets. Do you want me to give you, like, a hint on some specific tools that would help? Sure. [DING] OK, you have at your disposal some string, a mallet, a file, anything you would find in an office drawer. Isn’t the mallet metal? Yeah, but imagine that it’s not magnetic metal. There’s some metals that don’t stick to magnets. Yeah. Yeah, so imagine it is made of like something not magnetic, but it’s still hard. Maybe it’s like a rock mallet and a diamond file. It doesn’t stick to a magnet. OK, does it have to do with breaking it in two? OK. OK, so let me, like, break them in two. DIANNA: OK. Oh, I know. I break them in two. And then when I break them in two, then I suddenly have two pieces. And so I can tell which pieces are attracting each other or not. Now it’s possible that I could have two pieces that are not magnetized. I put them together, and nothing happens. Exactly. Yeah, if you could just break the iron bar. Just going from two to four. Yeah. So yes, OK. All right, yes, use the mallet. [NON-WORD SOUNDS] Break it in two. [NON-WORD SOUND] And then put two pieces together and see what happens. And then put another two pieces together. And then from there, I can figure them out. Ideally, like, probably I would have labeled them, right? Magnetic, not magnetic. We’re in an office. You have a pen. OK, but I could always go back and reconstruct. Or, we’re YouTube. You have a label maker. OK. OK, yes. DIANNA: Here’s a challenge for you at home. It’s really hard to break iron, and we don’t know how thick the bars are. So if you can’t break them with the mallet, how else could you tell which is the magnet? Let me know in the comments, and I’ll leave a comment a day after this video goes up with all the ideas I have and some of the top ideas you write down below in the comments for how you could do this. Yes. Good. Thank you so much. That was super fun. Sure. Well, thank you. That was lots of fun. I agree. That was really, really fun. I enjoyed it a lot. I appreciate that you took time out of your incredibly busy schedule to answer ridiculous physics riddles on “Physics Girl.”Thank you. It was a lot of fun. It was great to have you. Thank you so much for watching and– Happy physics-ing! [MUSIC PLAYING]


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