Since the normal force and the force of the box acting on the plane are the same, we can reference the force against the plane as the normal force. When an object is placed on an inclined plane, its w...Since the normal force and the force of the box acting on the plane are the same, we can reference the force against the plane as the normal force. When an object is placed on an inclined plane, its weight vector can be resolved into the normal force, which is equal to the force of the object perpendicular to the plane, and a parallel force, which pushes the object down the inclined plane.