So, that's -- does anyone know which classical law of motion that would be?

你们有谁知道这是,哪个经典运动定律吗？

麻省理工公开课 - 化学原理课程节选

For example, suppose you use vertical motion and you use y instead of x; and a would be g or -g; that's a particle falling down under the affect of gravity.

例如,假设在竖直运动中,你用 y 来代替 x,那么 a 就是 g 或者 -g,这就是一个受重力作用下落的质点

耶鲁公开课 - 基础物理课程节选