更新1:
what means how long does it remain in the air? please advise me 中文??
更新2:
i dont understand 1s x 2 = 2s??
PHYSIC 問題
2012-05-03 8:52 pm
A child jumps vertically upwards, leaving the ground with speed 9.81ms^-1, How long does it remain in the air? For the purposes of this question, you may treat the child as particle, subject only to the downward force of gravity. Please aadvise me more details! Thanks!
回答 (1)
2012-05-03 11:27 pm
✔ 最佳答案
You are asked to find the time interval between the child leaves the ground and when he hits the ground again.Use equation of motion: s = ut + (1/2)at^2
with s = 0 m, u = 9.81 m/s, a = -g (= -9.81 m/s^2), t =?
Hence, 0 = (9.81)t + (1/2).(-9.81)t^2
i.e. t = 2 x 9.81/9.81 s = 2 s
Therefore, the child remains in air for 2 seconds.
收錄日期: 2021-04-29 17:46:53
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120503000051KK00212