Constant-Acceleration Motion

Core Sentence / 核心句

Constant-acceleration equations are integrated consequences of one assumption: acceleration is constant over the interval.

中文理解：四个公式不是互不相关的记忆块，而是同一个恒加速度假设的积分结果。

v = v_{0} + a t

x = x_{0} + v_{0} t + \frac{1}{2} a t^{2}

v^{2} = v_{0}^{2} + 2 a (x - x_{0})

v_{avg} = \frac{v _{0} + v}{2}

先验证 $a$ constant，再选不含多余未知量的式子。公式里的 sign 来自坐标系。