I’m very tired, ______ I need to have a 发布时间:2017-06-19 13:42 │ 来源:www.tikuol.com 题型:选择题 问题: I’m very tired, ______ I need to have a good rest. [ ]A. because B. so C. but D. then
题型:选择题 (1)在氢原子光谱中,电子从较高能级跃迁到n=2能级发出的谱线属于巴耳末线系.若-群氢原子自发跃迁时发出的谱线中只有2条属于巴耳束线系,则这群氢原子自发跃迁时最多可发出______条不同频率的谱线.(2)一个物体静置于光滑水平面上,外面扣-质量为M的盒子,如图1所示.现给盒子一初速度v0,此后,盒子运动的v-t图象呈周期性变化,如图2所示.请据此求盒内物体的质量. 查看答案