The lob in tennis is an effective tactic when your opponent is nearthe net. It c

Question

The lob in tennis is an effective tactic when your opponent is nearthe net. It consists of lofting the ball over his head, forcing himto move quickly away from the net (see the drawing). Suppose thatyou lob the ball with an initial speed of 14.5 m/s, at an angle of 50.5° above the horizontal. At this instant youropponent is 10.0 m away from the ball. He begins moving away fromyou 0.30 s later, hoping to reach the ball and hit it back at themoment that it is 2.10 m above its launch point. With what minimumaverage speed must he move? (Ignore the fact that he can stretch,so that his racket can reach the ball before he does.)

Explanation / Answer

Let t be the time needed for the ball to fly up and then back tothe height of 2,1 m above launch point. 2,1=vsint-gt^2/2=14,5*sin50,5*t-gt^2/2 solve this equation we have t=2,077(m/s). the horizontal distance of the ball now is x=vcos50,5t=19,15 Let the velocity of the man be v, in the least condition; v*(2,077-0,3)=(19,15-10) so v=5,15m/s

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.