a physics mc quesion about mechanics...

2007-09-16 1:56 am

An object passing a mark with a velocity ym/s eastward is subjected to a constant acceleration of x ms^-2 in a westward direction. How long, in seconds, will it take to return to the same mark?

一物體受到向西之恆加速度xms^-2作用，並以ym/s 的速度越過目標。求物體需時多久才能返回相同的目標？(以s為單位)

回答 (1)

用戶79672

2007-09-16 2:02 am

✔ 最佳答案

SIMPLE THINKING

When the object pass a mark again, the velocity is same as -ym/s
then by time = 2y/x

2007-09-15 19:27:31 補充：
This is MC question, so I need to think up the answer as fast as possibleThis method is the fastest method I think其實，問題本身跟向東、向西，冇乜關係可以話向上、向下thinking by conversation of energy.. so when the object pass a mark again, the velocity is same as -ym/s

2007-09-15 19:27:49 補充：
如要計出來by u^2-v^2 = 2asnow s = 0so u=-v(I like your name...Jasmine)

2007-09-15 19:28:54 補充：
why the object pass a mark again, the velocity is same as -ym/s？？ The velocity is not sameThe speed is same but the direction is opposite

參考: 膠

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