※ 引述《johnnycool (奋战的盛夏光年)》之铭言： : 各位大大好 : halliday 第7板 : 77页的18题 : 还有78页的23题 : 我不太会做 : 可否帮我解答一下 : 三Q ----------------------------------------------------------- 1.77页的18题 In the 1991 World Track and Field Championship in Tokyo, Mike Powell jumpped 8.95m, breaking by a full 5 cm the 23-year long-jump record set by Bob Beamon. Assume that Powell's speed on takeoff was 9.5m/s (about equal to that of a springter) and that g=9.8m/(s^2) in Tokyo. How much less was Powell's horizontal range than the maximum possible horizontal range for a particle launched at the same speed? Sol:一粒子，初速 9.5m/s 45度 斜向抛射，有最远射程 9.21m 比 Powell 多了 9.21-8.95=0.26m 2.78页的23题 A certain airplane has a speed of 290.0km/h and is diving at an angle of θ=30.0度 below the horizontal when the pilot realesed a rader decoy. The horizontal distance between the realese point and the point where the decoy strikes the ground is d=700m. (a)How long is the decoy in the air? (b)How high was the release point? Sol: 290 km/h = 290*1000/3600 m/s = 80.56 m/s 水平初速=80.56．cos(30度)=70 m/s 向右 垂直初速=80.56．sin(30度)=40 m/s 向下 (a) 70 ．t =700 ∴ t = 10 s (b) h= 40t + 0.5g(t^2) = 897 m --

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