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

Question

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 thedrawing). Suppose that you loft the ball with an initialspeed of 15.0m/s at an angle of 50.0o above thehorizontal. At this instant your opponent is 10.0m away fromthe ball. He begins moving away from you 0.30s later, hopingto reach the ball and hit it back at the moment that it is 2.10mabove its launch point. With what minimum average speed musthe move? (ignore the fact that he can stretch, so that his racketcan reach the ball before he does.) answer: 5.79m/s

Explanation / Answer

set up the equations of motion of the tennis ball: ay=-9.8 hy=-4.9t2+15t*sin50 vx=15cos50 hx=15t*cos50 the other player hits the ball when the ball is at Hy=2.1: hy=-4.9t2+15t*sin50=2.1 t=2.15 seconds we need to find the horizontal distance Hx of the ball at thistime: hx(2.15)=15(2.15)*cos50=20.7m so the other player must cover 20.7-10=10.7 meters in 2.15-.3=1.85seconds. this is an average speed of 10.7/1.85=5.78 m/s

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

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