 Hi, I'm Ashley from the North Carolina School of Science and Mathematics. Today we are going to talk about forces, what they are, how they affect us, and all the things around us. We'll learn what balanced and unbalanced forces are as well as something called inertia. We'll show you how to conduct your own experiments so you can investigate and learn more about forces in motion on your own. To do the experiments in this video you will need the following. Construction paper, straws, tape, and round candies with holes in the middle of them. First, we need to learn what forces are and what it means when they are balanced versus unbalanced. Forces are things like gravity, momentum, and friction. Something that has equal forces acting upon it stays at rest. Something that has unbalanced forces acting upon it moves. Let's try an easy experiment to see how this works. This is a plastic container with a small hole in the lid. We tied one end of a rubber band inside, basting it to the lid. When we take the container and hold it up by the band, what forces are acting on it? Pulling down on it is gravity. The rubber band exerts its own force from the top, keeping the object from being pulled down to the ground by the gravity of the earth. The force of gravity pulling the object down and the band holding it up are the same. So would you say the forces are balanced or unbalanced? Since it doesn't fall or float up, the forces are balanced. Now, what happens if you cut the rubber band? Obviously, it fell to the ground because the gravity of the earth pulled it down. When the band was cut, the forces became unbalanced, allowing gravity to take over and pull downward on the container. Here's one you can try yourself. Put your hands together and push them equally towards one another so nothing moves. By doing this, you've achieved a balanced force and your hands and arms stay right where they are. Push harder with one hand than the other so they move. That's an unbalanced force. You've got the basics of the idea between balanced and unbalanced forces. Now, let's learn about something called inertia. Basically, objects tend to do what they're already doing. Inertia means that an object will always continue moving at its current speed and direction until some other force causes its speed or direction to change. The same goes for objects that are not moving. An object will remain at rest until some force makes it move. So there are two states of inertia, the state of rest and the state of moving. Sometimes it's hard to see inertia because of a force called friction. Friction is what causes objects in motion to stop moving. Try rubbing your hands together. What do you feel? They start to feel warm because your two hands rubbing together create friction giving off heat, which is the kind of energy. The faster you rub your hands together, the more friction and heat you create. When you slow down, you create less friction and heat. Think of the brakes you use to stop your bicycle. The friction of the brakes on the wheels stops them from turning and counteracts the inertia moving the bike and rider forward. Another example would be when you ride a skateboard, you have to keep kicking to keep it moving. Why is that? Because friction between the wheels and the road make it slow down and you use your foot to keep it moving. In other words, friction between two or more moving objects decreases the speed of these objects until they stop moving and reach the point of rest. Let's talk about the famous scientist, Sir Isaac Newton. He helped explain inertia and what is called Newton's First Law. A body remains at rest or in motion with a constant velocity unless acted upon by an external force. What this means is that an object at rest won't move unless another force makes it move and an object in motion will continue moving unless some other force stops it. Here's an illustration of what we're talking about. When the duck is not moving at all, is it affected by a balanced or unbalanced force? Balanced. When it gets a push and starts on the ramp, is it balanced or unbalanced? Unbalanced. The duck stops at the bottom. Why? Because the board at the end of the ramp stops it. So does that make it balanced or unbalanced? Balanced. If there was nothing to stop it, the duck would keep moving. Would the forces be balanced or unbalanced? Unbalanced. Remember talking about two states of inertia, the state of moving and the state of rest? If the duck kept going with nothing to stop it, which state of inertia is it in? The state of moving. When the duck stops, what state of inertia is it in? The state of rest. Now let's try our own experiment with something you can make yourself with a few simple items. We're going to build a sail car that will move when you blow on it. You will use your stiff construction paper, straws, tape, and four lifesaver type candies for each car. It's fun to try this with your friends and see how different designs and different ideas affect how fast and how far the car moves when you blow on it. Have a race. How far did your car go? How fast did it travel? Who won the race? The car didn't move until you blew on it. By blowing on the car, you create an unbalanced force. So what have we learned? We learned about forces, something that pushes or pulls on an object. We learned there are two types of forces, balanced and unbalanced. What happens when the forces on an object are unbalanced? The object stays put. It doesn't move. What happens when the forces are unbalanced? The object moves. Something else we learned about was inertia. Inertia is the idea that objects tend to do what they are already doing. An object will continue moving in its current speed and direction until some other force causes its speed or direction to change. In other words, objects that are not moving won't move unless something else makes them start moving. This idea became Newton's first law of motion. Good luck moving forward as you learn more about forces, motion and inertia in school and on your own. Thanks for watching!