 spring the snow has melted. It's time to get outside and make some circles. So what kind of circles do I like to make? I like to make circles on bikes. When a bike's moving in a circle the thing that keeps it going in a circular path is friction. So we could say that the force of friction is acting like a centripetal force. That means that when we go and do the math we're going to start off by saying FC equals FF and this is how we start a lot of these problems is by saying centripetal force FC equals some other type of force. We're gonna see a couple others here today. You know what else I love to do is I like to tie a ball to a string and swing it in a circle. This ball is going in a horizontal circle and the reason it goes in a circle is because this centripetal force is supplied by the force of tension in the rope. We can swing that ball horizontally like this or we can swing it vertically like that. In this situation the force of tension is supplying the centripetal force but the force of gravity also works to make a centripetal force as well. This situation is a little trickier as it involves a net force but we'll tackle it in a future video. You know what else is good to do in the springtime? Going on a roller coaster. In a roller coaster loop the loop. When I'm moving in a circle and I'm at the top of the circle then the centripetal force is just the force of gravity. If I'm moving at minimum speed the slowest speed possible to make it through the loop in the roller coaster. You know what else is good to do in springtime? Going into outer space and orbiting around the earth. When a satellite orbits a planet the force of gravity is a centripetal force. Gravity is the force that pulls the object back towards the center of the circle. So when we do a calculation we're going to make FC equal to FG. In the next couple of videos I'm going to show you the calculations to solve for some of the variables and values we can talk about in this intro video today.