Re: [問題] 有關halliday裡面的題目
※ 引述《johnnycool (奮戰的盛夏光年)》之銘言：
: 各位大大好
: halliday 第7板
: 77頁的18題
: 還有78頁的23題
: 我不太會做
: 可否幫我解答一下
: 三Q
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1.77頁的18題
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 斜向拋射，有最遠射程 9.21m
比 Powell 多了 9.21-8.95=0.26m
2.78頁的23題
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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