A net force is defined as the sum of all the forces acting on an object. The equation below is the sum of N forces acting on an object. According to Newton’s Second Law, when an object accelerates, then there must be a net force acting on it. If the net force acting on an object is zero, then the object is not accelerating and is in a state that we call equilibrium. For example in free fall, the net force on an object equals its weight – the one force pulling on it.