 My name is Katie, and I am a children's librarian at the San Francisco Public Library. For today's STEM challenge, we're gonna be making balloon cars. So before we get started, I just wanna make sure everyone knows what STEM is. STEM is an acronym that stands for Science, Technology, Engineering, and Math. So what makes these awesome little balloon cars a STEM program? Well, it all has to do with the science behind potential and kinetic energy. What happens is as this balloon inflates, the air inside is stored as potential energy. And potential just means that it has the ability to do something in the future, but it's not doing it right now. And then once the air we let it go, it turns into kinetic energy. And kinetic energy is the energy of movement. So what happens when we turn it from potential to kinetic, the car should move. All right, let's get started. What we need to make a balloon car are two straws, a tongue depressor, which is really just a wide popsicle stick, two wooden dowels, a balloon, and four wheels. So our first step here is we're gonna take one of the straws and we're gonna cut two little pieces, just wide enough to fit across the width of the tongue depressor. And if it's a little bit wider or more narrow than the tongue depressor, that's fine. We just want to make sure we can get it taped on there correctly. We'll do one, oops. Okay, let's try another one this way so we don't fling it. And then we'll do another one about the same length. So we have our two little straw pieces. We're gonna take the first piece and we're gonna tape it along the width of the tongue depressor, about a third of the way up. And what we wanna do is make sure that we can get it as straight up and down across the top as possible. Otherwise our wheels are gonna be a little bit crooked and our car will be funky. I'm gonna make sure you have a piece big enough to go over the top of the straw and across the top of the tongue depressor. And we're gonna do the other side, nice long piece here. Sometimes it helps if you put it on the straw first and then place it on top of the tongue depressor. And the second one's gonna go about two thirds of the way up. So we have a nice balance for our wheels. All right, we're gonna set that aside and then we're gonna move on to the balloon. So with the balloon, before we get started with this part, I like to give it a few just stretches. It just kind of makes it easier to inflate later. Then we're gonna take our uncut straw and we're going to insert it into the bottom of the balloon just about to where it starts to widen at the base of the balloon. We kind of wanna give it a little wrap. And then we're gonna tape the bottom of the balloon to the straw. We're gonna try and make it air tight. We don't want any air to escape out of that straw. And it doesn't have to be pretty. We just wanna make sure it's tight. Okay, so we're gonna test it. And the way that we test it is we inflate it with the straw. And what'll happen is if any air escapes or if it doesn't inflate, then we need to give it some more tape. If no air escapes, then we're good to go. So let's give it a shot. Put our finger over it. No air is escaping. We are good to go. So we're gonna put that down and go back to our tongue depressor. And our next step is we're gonna take wooden dowels and we're gonna put it right into the straw here. We're gonna push it through so that the dowel is sticking out of both sides of the straw. And then we're gonna take one of our wheels and just pop it on the end of the dowel. And then we're gonna take another wheel and we'll pop it on the other side. And if you need to, for some reason it's a little too loose, you can always put some tape on the edges here. And then we're gonna take the other dowel and do the same thing on the other side. Right through the straw. Make sure it's sticking out on both sides. Pop the wheel on and then the fourth wheel. All right, hey look, it kinda looks like a car. All right, we're to our last step here. We're gonna take our straw with our balloon and we're gonna tape it to the top of the car. So you wanna make sure that the wheels are bottom side down and then we'll just get a few pieces of tape here. And you wanna tape it so that it sticks over the edge of the tongue depressor, just enough to blow up the balloon so that you don't put your mouth on the wooden part of the car. Couple pieces here, right around the middle there. And then just one more for funsies at the end. Make sure it's nice and stable. This is a balloon car, okay? So let's give it a shot and see what happens. All right, we cut all of this potential energy in here. I'm gonna let it go and see what happens. It went all the way. So before we go, I have a couple questions for you. What do you think would happen if you made the balloon really big or really small? How do you think it would affect how fast the car goes or how much farther it would go? And finally, would you let the pigeon drive the balloon car? Thanks for joining me today.