 Welcome back to Kids Fun Science. My name is Ken and today's experiment is the rollback can. As always, adult supervision is required. What you need for this experiment is a can with a lid, a screwdriver, a 9-volt battery, rubber band, tape, and two paper clips. I'm going to do this experiment backwards where I'm going to show you the experiment first and then show you the procedures on how to put it together. The reason the can moves backwards is the transition of the potential energy to the kinetic energy. In this case, the can, the kinetic energy is transformed into an easy observable example of elastic potential energy, which is then transformed back into kinetic energy. The way this works is when I roll the can forward, I give the can kinetic energy. Gravity exerts a lot of force on the heavy battery pulling it down and causing the resist the twisty motion of the rubber band. As the can rolls forward, a stubborn heavy battery doesn't turn with it, so the rubber band gets all wound up. This converts the can kinetic energy into potential energy, and once all the kinetic energy is used up, the rubber band can untwist, pushing against the battery and rolling the can back towards you. Potential energy turns back into the kinetic energy. Pretty awesome, as I thought it just had a great back spin. Now you've seen this awesome experiment, now I'm going to show you how to put it together. I use a Folger's Coffee Cup, 11 ounces, 320 grams. You're going to make sure it's empty, then you're going to poke a hole through the bottom of the can. I just use a regular screwdriver. You can use anything, just be careful not to stab yourself, and then take the top part of the coffee can or any kind of can and poke a hole through that. Now you take your 9-volt battery and put a rubber band on the top and place it over with tape. I'm using Blue's Paters tape. Then take your rubber band and bring it to the top of the other side and bring the tape down so it's secure. You can use any kind of tape, as long as it's flipped right over and the battery looks like this at the end result. Now you're going to pick this battery and rubber band and place it towards the bottom of the can. The rubber band is kind of like lining over the hole. Now you're going to take your screwdriver and push that rubber band all the way through the bottom part of the hole, and then you're going to grab that rubber band from the other side and pull that out. Once you do that, pull the screwdriver out. Now you're going to take one of your paper clips and you're going to put it between the rubber band right there, just like this, and then pull down on the rubber band, the inside of the can, so it's secure on the bottom there. Now that's the easy part. Here comes the hard part. Now you can grab the other side of the rubber band and you're going to pull it up and grab about halfway down right there, and then you're going to take the lid and you're going to put the rubber band right in front of the hole, just like this, and then you're going to take your screwdriver again and you're going to push that through the hole right there, and then hopefully you get enough of the rubber band so your fingers can grab it to pull it through. Put the lid completely on while you're still holding the rubber band, and then you're going to take your second paper clip and do the same exact as the bottom, put it through the rubber band, and now it's secure. Now you have your rolling cap, so now all you have to do is be able to roll it. So that's how you put it together. I hope you enjoyed this video. Remember to click thumbs up below and to subscribe. Thanks for watching.