What is Circular Motion?

In the field of physics, circular motion is a term that defines an object’s movement in a rotating manner. In this motion, an object navigates around a circle, such as the planets moving around the Sun in each of their orbits. The object also moves around its center at an equal distance, but accelerates as it goes around in order to maintain a circular motion.

One important element that makes circular motion possible is an inward force; this is also called the centripetal force. According to Newton’s Law of Motion, an object generally requires a certain force acted upon it for the object to move, accelerate, and react. In circular motion, the absence of the centripetal force will make the object move only in a straight line because there is nothing that pulls the object inward. For example, a pebble tied to a string can be swung continuously because the string pulls the pebble toward the center. The pebble falls straight to the ground, however, when the string is cut.

A circular motion has two kinds: uniform and non-uniform. In uniform motion, the object travels along at a steady speed. This does not take into account the object’s velocity, which is the change of speed or direction, because a rotating object is always changing its direction.

A non-uniform circular motion, on the other hand, makes an object move in shifting speeds. The distance between the object and the center of the sphere also changes. The velocity of the object will increase if the distance is smaller, while a greater distance slows down the rotation of the object. For example, the pebble attached to the string will spin faster if the string is shorter, but will spin at a slower rate if the string is longer. This is because the force acting upon the object becomes either weaker or stronger when the distance is longer or shorter, respectively.

Everyday situations where uniform and non-uniform circular motions apply can be found in a carnival rides. A Ferris wheel travels in a uniform motion because the wheel moves at a constant speed and maintains the same distance from the center. The roller coaster, on the other hand, is a good example of a non-uniform motion, where the carts go up slower than when they are falling down. The size of the circles the carts go along also accounts for the change of velocity.