The lob in tennis is an effective tactic when your opponent isnear the net. It consists of lofting the ball over his head,forcing him to move quickly away from the net (see the drawing).Suppose that you loft the ball with an initial speed of 15.0 m/s atan angle of 50.0° the horizontal. At this instant your opponent is10.0 m away from the ball. He begins moving away from you 0.41 slater, hoping to reach the ball and hit it back at the moment thatit is 2.10 m above its launch point. With what minimum averagespeed must he move? (Ignore the fact that he can stretch, so thathis racket can reach the ball before he does.)
