I asked T -Rex to tell me what force pulls the swing back down. He knew it is gravity. Then I asked, "Why does the swing keep going at the bottom of its path, and start moving up?" He was puzzled.
I told him that it is because the swing is already moving. If something is moving, it will keep moving until something stops it. He smiled.
I asked him again just now if he knew why the swing keeps going. He answered , "Because it was already moving." Yay!
Newton's First Force Law says that a thing will keep moving at the same speed and in the same direction, unless something stops it. This tendency to keep doing the same is called inertia.
Centrifugal (center fleeing) motion is sometimes credited to a force with the same name. You are not likely to see such a force, and if you did, it would have another name. The movement away from center is due to inertia.
The vast majority of circular systems depend on a centripetal (center seeking) force, in this case the rope, and inertia.
Here is a challenge for you. Find some circular motion examples and figure out what the centripetal (center seeking ) force is.
I would Love to hear what you find!