It's OK to use certain fundamental constants that come in a lot of calculators, so there's nothing we can do about that. That's OK.

当然允许使用,一些普通计算器里都有的基本常数，我们不会连这些都不让用，这是没问题的。

麻省理工公开课 - 化学原理课程节选

So you cannot use the formula once it hits the ground because once it hits the ground, the fundamental premise that a was a constant of -9.8 or -10 is wrong.

当物体落地以后,该公式就不适用了,因为当物体落地后,公式的基本前提——,加速度为常数-9.8或-10——就不成立了

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