If you give a sign, on top of the number, that takes care of all ambiguity in one dimension.

如果你在数字前加一个符号,就把一维运动的所有的歧义解决了

耶鲁公开课 - 基础物理课程节选

We said, "Let's take, for the simplest case that we can possibly imagine, namely a particle moving in one dimension along the x-axis with a constant acceleration a.

我们说过,"考虑我们可以想象的最简单的情况,即质点在一维空间运动,沿着 x 轴且保持恒定加速度 a

耶鲁公开课 - 基础物理课程节选