Work Step by Step
If the acceleration of an object is zero, Newton’s second law tells us that the NET force, or vector SUM of the forces acting on it is zero. However, there can be multiple forces acting on the object, as long as they sum to zero. For example, a child sitting on a chair is pulled downward by gravity and pushed upward by the normal force from the chair, but she has zero acceleration. The 2 forces are equal in magnitude and opposite in direction.