Force is a push or pull on an object, characterized by magnitude and direction, with its SI unit being the newton (N). It can be categorized into contact forces, such as friction and tension, and non-contact forces, including gravitational and electromagnetic forces. Centripetal force, an external force directed toward the center of a circular path, maintains circular motion. Conversely, centrifugal force acts outward, opposing centripetal force, and is crucial in devices like cream separators. Among the four fundamental forces—gravitational, electromagnetic, weak nuclear, and strong nuclear—gravitational force, though weakest, has an infinite range, while the strong nuclear force is the strongest but short-ranged, crucial for atomic nuclei cohesion.