Answer
a. It has the same speed.
b. It is slower.
Work Step by Step
a. With no air resistance, the ball will have the same speed $v_o$ but its velocity is directed downward. This can be seen from equation 2.13. If the displacement is zero, under movement with constant acceleration, the speed does not change.
b. With air resistance, the ball returns to its initial height moving more slowly than it started. On the way up, air drag acts downward on it, acting in concert with gravity to slow it down, so it won’t go as high as in case A, with no air resistance. It then drops down, from that lower height, reaching its initial position with a slower speed than in case A (and air drag slows it down even further).
