04. The 1992 world speed record for a bicycle(human powered vehicle) was set by Chris Huber. His time through the measured 200m stretch was a sizzling 6.509s, at which he commented, "Cogito ergo zoom!" (I think, therefore I go fast!). In 2001, Sam Whittingham beat Huber's Record by 19.0 km/h. What was Whittingham's time through the 200 m ? 10. Panic escape. Figure 2-22 shows a general situation in which a stream of people attempt to escape through an exit door that turns out to be locked. The people move toward the door at speed Vs = 3.50 m/s, are each d = 0.25 m in depth, and are seperated by L = 1.75 m. The arrangement in Fig. 2-22 occurs at time t = 0. (a) At what average rate does the layer of people at the door increase? (b)At what time does the layer's depth reach 5.0m? (The answers reveal how quickly such a situation becoms dangerous.) Fig. 2-22: |← L →|d|← L →|d|← L →|d|← L →|d|← L →|d|← L →|d _________________________________________________________________ | 人 人 人 人 人 人 人 | ←封死的 _________________________________________________________________| 逃生门 L : 人与人的间隔 d : 人的「厚度」(翻的好怪 = =") (注: 这题真的满生活化的, 尤其是算完後就知道逃生梯放置物品真的会害死人...) 30. A world's land speed record was set by Colonel John P. Stapp when in March 1954 he rode a rocket-propelled sled that moved along a track at 1020km/h. He and the sled were brought to a stop in 1.4s.(See Fig. 2-7 ←图不 重要) In terms of g(重力加速度, 打不出斜体字 :p ), what acceleration did he experience while stopping? CH3 → 35. Three vectors are given by a = (3, 3, -2) → b = (-1, -4, 2) → → → → c = (2, 2, 1) Find (1) a‧(b X c) → → → (2) a‧(b + c) → → → (3) a X (b + c) 72. A fire ant, searching for hot sauce in a picnic area, goes through three displacements along level ground: → d1 for 0.40m southwest → d2 for 0.50m due east → d3 for 0.60m at 60 degree north of east. Let the positive x direction be east and the positive y direction be north. What are (a) the x component and → (b) the y component of d1 ? What are (c) the x component and → (d) the y component of d2 ? What are (e) the x component and → (f) the y component of d3 ? What are (g) the x component, (h) the y component, (i) the magnitude, and (j) the direction of the ant's net displacement ? If the ant is to return directly to the starting point, (k) how far and (l) in what direction should it move ? (这题很烦...) 如果有看不懂的字 也许是我打错了 请尽快提出~ 并请有题目的同学帮忙校对一下~ -- ★ Mr. wind http://meteorologytoday.googlepages.com/mr.wind (天气资讯连结总整理) --

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