 Welcome back to Kids Fun Science. My name is Ken. Today's experiment is the coffee cup pendulum. What you need for this experiment is 15 washers, string, pencil, and a coffee cup. Please help us reach 20,000 subscribers by subscribing and sharing. Thank you. All right, welcome back to Kids Fun Science. Today we're going to do the pendulum experiment. So what I have here is a whole bunch of washers on one end of the string and then a single washer here. And then you have to make a prediction. If I put it over my finger with the large washers on the end here and hold the single washer here, when I let go of the single washer, what is going to happen? It stops right before it hits the table, right? So you thought it probably was going to hit. Most people do, but it stops every time you do that. Do it one more time. Here it goes. It stops right there. It's pretty cool. So how it works is when you let go of the washers here, you get an acceleration coming down. At the same time, when the pendulum, the single washer swings, you get rotational energy coming. And as it comes down and starts to wrap around, you add a little bit of friction as it goes each time around. And that's what stops it of acceleration going down and halts the washers right there. So that's the science behind it. Now let's try something a little bit more different. Let's take a coffee cup, right? Ceramic coffee cup and some washers at the end here. So when we lean it over and we'll do a side shot here, we lean it over and I'm going to let go. Now you have to make the same prediction. Is it going to break or is it going to stop again? Yeah. It stops again, right? Even though the coffee cup is right there, it still stops, which is pretty cool. Because once again, the acceleration coming down, but you have the rotational energy going around, and then you combined it with the friction as it goes around. And it stops the coffee cup down, which is pretty cool. So I placed a piece of pink paper on the washer so you could see the washers swing in slow motion and you could see how the rotational energy picks up. And then the friction brings the coffee cup to a hall. You could also do this on a pencil. It's pretty cool. Let's do it one more time. That's awesome. I love it. So one of the secrets that has been found out here is whatever your end is, if it's going to be, if it's the washers here, a number of washers to the one washer, it's a 14 to one ratio. So you're going to want 14 washers here and one washer here and about a 25 to 30 inch piece of string. Now for the coffee cup, we do the same thing. And so you kind of have to have a scale. So it's a 14 to one. So I have a 14 ounce coffee cup. So I have 1.4 ounces on this end of washers. So I have a scale. So I was able to figure that out. And then I got about a 26 inch piece of string. Therefore it allows it to do its science. And that is a coffee cup pendulum experiment. Please make sure you like and subscribe as we're trying to get to 100,000. And thanks for watching.