Question

In which type of motion a particle or a system of particles move around a fixed axis?

Answer 1

In order to answer this question, we will first mention the type of motion in which a particle or a system of particles move around a fixed axis. And then we will discuss much more about that motion with a perfect example.

Complete answer:
Anything that spins or moves in a circular route is said to be in rotational motion. It's also known as circular motion or angular motion. The motion can be uniform or non-uniform (i.e., the velocity $v$ does not change), but it must be circular. Consider a football that spins like a top while also arcing in the air, or a wheel rolling down the road. Scientists view these types of motion separately because they require separate equations (albeit they are closely equivalent) to analyse and explain them.

It's actually beneficial to have a separate set of measurements and calculations to describe
rotational motion of those objects rather than translational or linear motion, because you'll often get a quick refresher in subjects like geometry and trigonometry, which are always useful for the science-minded. For simplicity, the Earth's and other planets' revolutions around the sun are treated as circular, yet planetary orbits are elliptical (slightly oval) and hence not examples of rotational motion.

Hence, in rotational motion a particle or a system of particles move around a fixed axis.

Note: Every point in the body moves in a circle around the axis of rotation in rotational motion around an object's centre of mass. The centre of mass of an item is the place from which an equal quantity of mass is distributed in two opposite directions.