✔ 最佳答案
a)
Since s = ut + 1/2 at^2,
(10 - 1) = 1/2 (10) t^2 (u is initial velocity which is 0 m/s this time)
t = 1.341640786s
It is the time for the man to jump from the 10m building to 1m high of cushion.
v = d/t
=1/1.341640786
=0.745355992 m/s
As the cushion is placed at 1m away from the building, it is the min. speed of the man could jump.
v = d/t
=(1+6)/1.341640786s
=5.217491948 m/s
As the longest distance of cushion is 7m away from the building, it is the max. speed of the man could jump.
b)
Since s = ut + 1/2 at^2,
(10 + 10 - 1) = 1/2 (10) t^2 (u is initial velocity which is 0 m/s this time)
t = 1.949358869s
It is the time for the man to jump from the 20m building to 1m high of cushion.
v = d/t
=1/1.949358869
=0.512989176 m/s
As the cushion is placed at 1m away from the building, it is the min. speed of the man could jump.
v = d/t
=(1+6)/1.949358869
=3.590924232 m/s
As the longest distance of cushion is 7m away from the building, it is the max. speed of the man could jump.
2010-11-11 22:09:01 補充：
雖然答案跟你的不一樣, 但我認為你的答案是錯的。
正常b)的答案比a)小, 因為b)那人在更高的地方開始跳, 那他下降到cushion的時間一定比a)長, 如果cushion是1m away, 那他的min speed 一定會更小, 因為vt=d, 現在d是1m, b)的t比a)的長, 所以b)的v一定比a)的v小。
2010-11-11 22:46:19 補充：
那你知道計到的答案跟我一樣嗎?
2010-11-11 23:35:57 補充：
所以有時盡信書不如無書。
