In physics, force is defined as a vector quantity representing a push or a pull that acts upon an object. It is a fundamental measure of interaction that, when unopposed, can cause an object to accelerate or change its state of motion. Forces are quantified in the SI unit of Newtons (N) and are central to the study of mechanics. Various types of forces exist, including gravitational force, tension, friction, and electromagnetic force. The relationship between force, mass, and acceleration is a foundational principle, establishing that the net force acting on an object is directly proportional to the object's mass and acceleration.