When an object is thrown upward, the gravitational force acts against its displacement. So, the work done by the gravitational force is the dot product of the gravitational force and displacement vectors. Since these vectors point in opposite directions, the work done is negative. The gravitational force does work on the object by transforming the objects' kinetic energy to potential energy. After reaching the maximum height, the object falls back. The gravitational force acts in the direction of the displacement, and the work done is positive. Suppose an object is lifted, both the applied force and the gravitational force do work on the object. The net work done on the object is given by the work-energy theorem. If the object is stationary before and after a lift, the net change in kinetic energy is zero. So, the work done by applied force is negative of the work done by the gravitational force.