昨天晚上7点钟，我不在写家庭作业。

I wasn't doing my homework at 7 last night.

youdao

我正在看一本书，我不在写。

I'm reading a book. I'm not writing.

youdao

先生——我写这几句话是为了告诉你，我的女儿现在已经不在我这儿了，我也不知道她什么时候回来，只要她回来了，我就写信告诉你。

SIR I write these few lines to say that my Daughter is away from me at present, and I am not sure when she will return, but I will let you know as Soon as she do.

youdao

I don't know where that is, that disappeared on the blackboard, then putting the time equal to 1 second into this formula.

我不知道我写在哪儿了,已经不在黑板上了,然后把时间等于1秒代入方程

耶鲁公开课 - 基础物理课程节选