Classical central-force problem

Imagine you are playing with a yo-yo, and you want to make the yo-yo go in circles around your hand. The yo-yo is pulled towards your hand by a string, and the force that keeps it moving in a circle is called the "centrifugal force."

This is similar to what happens in the classical central-force problem, where a small object, like a planet or a comet, goes around a bigger object like a star. The planet is attracted to the star by a force called "gravity."

Gravity pulls the planet towards the star just like the string pulls the yo-yo towards your hand. But the planet also has a velocity, or speed in a certain direction, which makes it move in a circle around the star. This movement is called "orbiting."

The classical central-force problem is concerned with figuring out the shape and size of the orbit. Scientists use complicated math equations to calculate how strong the gravity is and how fast the planet is moving, and then they can determine the shape and size of the orbit.

Think of it like drawing a picture: you have to use a lot of lines and shapes to draw a complicated picture. Scientists use a lot of math "lines and shapes" to figure out the shape and size of a planet's orbit around a star.