 My name is Matt, and I am a 2020 Yale intern at SFPO. So for today, we will be doing a challenge of self-stem video, and today's trick, we will be doing Newton's coin trick. So for today, the materials that you will need will include a water bottle, $88 bill, and some coins. So have you ever really wanted to challenge a friend or even make a bet against him? Well, here's something you can do. You can challenge them to take this $20 off of this water bottle, but here's a catch. You can't make these coins fall off. So I'll give you a second to think. How could you possibly get this $20 off without making these coins on top fall off? So have you thought of a solution yet? Well, if not, I'll tell you the trick to it. So what you simply want to do is to put your finger right here and just quickly chop off the $20 bill. I like this. It's like that. You see the coins in the fall off. So now you might be wondering how the heck did a $20 bill fall off, but not the coins? Well, there are two things that explain this. First, we have Newton's first law, which can also be known as inertia. And second, we have friction. Okay, so why does inertia or Newton's first law of motion play a key role in today's trick? Well, first let's talk about what it is in the first place. So Newton's first law of motion states that an object will remain at rest unless there is an outside force strong enough to unbalance it. And inertia is the tendency for an object to stay at rest. That is why sometimes Newton's first law of motion is also known as the law of inertia because it involves the object staying still. And so for today, the reason why the coins did not fall off when I moved the $20 bill is because there was no outside force that was acting upon the coins. The only force I used was my, was my, from my finger and I used it on the $20 bill. I did not apply the force to the coins. An outside force or an example of another outside force that could be strong enough to move the coins will be like a gust of wind in my room. But in this case, there was no gust of wind. So that's why only $20 will fall off because there was only enough pressure or there was enough outside force that only acted upon the $20 bill and nothing else. Okay, so to sum everything up, basically why the coins did not fall off was because there was just simply no force applied to the coins. All of the force from my finger was applied to the $20 bill. And that's why there was no force strong enough to overcome the coins. Inertia was because there was just simply no outside force that even touched the coin. Okay, now let's talk about friction and why does friction play a key role in today's video. So first let's talk about friction. What is it? Well, friction can be defined as the force between two surfaces that rub against each other. So how exactly this friction, how is friction shown in today's trick? Well, the surface of the $20 bill had a go against the surface of the water bottle cap. And since the surface of the $20 bill and a cap were both smooth, it made it a lot easier when I chopped the $20 bill off. It was easier for it to come off. But why? Well, it's because since it was smoother, that means there was less friction, which means less resistance. So what would happen if I use something such as sandpaper instead of using a $20 bill? Well, it would be harder for me to chop it off because it has a rougher surface. And the rougher the surface, there's more friction, which means more resistance. Hey, y'all. Thanks for watching today's video. And I hope that you not only learned something, but also enjoyed it. If you liked the video, please make sure to check out other videos created by other yo interns and SFPO librarians. Thanks.