f.4,,,phy. mechanics.

2008-09-26 4:58 am

After takeoff, a jet airplane accelerates uniformly from 250kmh^-1, to 1000kmh^-1 in the first 150km it travels. Find the acceleration and the time taken in this part of the journy. Neglect the vertical motion of the airplane.

回答 (1)

Audrey Hepburn

2008-09-26 5:05 am

✔ 最佳答案

Initial velocity, u = 250 kmh-1 = 69.44 ms-1

Final velocity, v = 1000 kmh-1 = 277.78 ms-1

Distance travelled, s = 150 km = 150 000 m

By v2 = u2 + 2as

(277.78)2 = (69.44)2 + 2a(150 000)

Acceleration, a = 0.241 ms-2

By s = (u + v)t / 2

150 000 = (69.44 + 277.78)t / 2

Time required, t = 864 s

2008-09-26 19:04:59 補充：
有一噴射機，在起飛後，在最初的150 km的旅程中，它的速度由250 kmh^-1平均地加速至1000 kmh^-1。
試求旅程中，飛機的加速度，以及走過這段距離的所需時間。
可忽略飛機垂直方向的運動。

參考: Myself~~~

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