The work done is negative as the force is applied in the forward direction and the displacement of the hand is in the backward direction.
The work done is positive as the work is done on the baseball by Carlton. Moreover, both the force applied and the displacement of Carlton are in a straight line in the forward direction.
The work done in this case is zero as Carlton rides with constant speed, the Kinetic energy too remains constant and hence net work done is zero.
The work done in this case is positive as the work is done on the baseball by Carlton and as the velocity changes its Kinetic energy also varies wit it.
Also the force applied and the displacement of Carlton in this case are in the directed to the same path.
