来自《耶鲁大学开放课程：基础物理 第1集 第1集》
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and backward in time,也可以向前延伸 -
and it says that whatever seconds,不管时间取什么值 -
one second before you set your clock to 0,在零点前一秒时 -
it would've been on the ground.物体就在地面上 -
What it means is它的意义在于 -
if you'd release a rock at that location若在该处以特定速度抛出一个物体 -
one second before with a certain speed that we can calculate,这个速度可通过计算得到 一秒之后 -
it would've ended up here with precisely the position and物体会运动至我们设定的起点 -
velocity it had at the beginning of our experiment.并且速度为我们设定的初速度 -
So sometimes the extra solution is very interesting所以有时候这些增根的意义很耐人寻味 -
and you should always listen to the mathematics当你解出增根的时候 -
when you get extra solutions.别忘了想一想它的数学含义