 Hi, welcome to the MIX, the team center at the San Francisco Public Library. My name is Eliana and I am your humble host for our STEM Challenge Joseph series. In this series we have some fabulous librarians sharing fun and creative projects and experiments that you can try at home. Today's challenge, I think you're going to love it. Are you ready? Hello friends, hello everybody, I'm Mr. Joseph and today we're going to design a better parachute. In order to do that we need to understand two concepts, gravity and air resistance. Let me demonstrate that with two papers. So we're going to crumple this paper first and before I demonstrate gravity and air resistance let me ask you a question. Which one is heavier? That's a tricky question. In fact, both papers are exactly the same mass and the same weight but let's see what happens if I throw this crumpled one, okay? Now let's drop this one, that's probably the same height, it's slower. What's happening? So first we have gravity pulling both objects down but the other one it's slower. So it's still pulling down but it's much slower. What's happening is there's all this air underneath called air resistance and it's preventing pushing the paper up and preventing it from falling down fast. So remember that concept when you're designing your parachute. So let's get started and make a parachute. Start with a circle, draw a circle onto a plastic bag, cut it perfectly. Now fold it in half then fold it again so you have four equal parts. Now if you want more strings on your parachute you can actually fold it again. So we're just going to use four holes for this test and grab a pencil and just find the center between this point and that point and just pierce it with your pencil slowly. To make it bigger, so it's easier for you to tie, make it bigger just twist your pencil and there you have it. We have four holes that are equally distant on the circle, how awesome is that? Now tie the string on all those holes and you should have something like this. I've already started this earlier. Now we are going to tie those strings together so that we can hook our jumper and make sure they're all even and that's pretty even and I'm just going to tie them together with a simple knot and there you have it. And you can even see the air resistance, oops, our string fell up. Make sure to, here's a simple trick, if you can't put your string onto the hole, just lick it and since this hole is a little smaller I'm going to make it bigger to make it easier for me and again tie a knot. This time I'm going to double knot it because it came out, there's too much air resistance. So when, and then I'm going to tie my jumper, hello jumper, just grab any old toys or any object that has some kind of weight. You could also experiment with different weights and see how that resists the air. Will it be faster if it's heavier? That's a question for you my designers and now that I have my jumper ready. So air resistance, so when we drop the paper down the air resistance since the parachute or the paper is dropping downward the air resistance is pushing up the opposite from its drop. So if I move this this way the air resistance is coming that way. This is really fun. So we're going to test it, we're going to test our flight, our flight for a parachute flight so I'm just going to turn on the video so you can see how it flies. I hope you get to try this at home. Make some parachutes with different sizes with different materials and thank you so much for joining me back to Eliana. Thanks Joseph. So for your parachute design challenge make sure you try different materials, different weights and maybe color it, throw another design on top of it and see if that actually changes anything. For more info, tips and tricks about our STEM talent show self series including this experiment and others be sure to check out sfpl.org and stay STEM-tastic.