在研究平抛运动的实验中,可以测出小球经过曲线上任意位置的瞬时速度,实验步骤如下:
A让小球多次从同一位置上由静止滚下,记下小球经过卡片孔的一系列位置
B按照课本装置图安装好器材,注意斜槽末端切线水平,记下小球经过斜槽末端时重心位置O点和过O点的竖直线
C取下白纸,以O点为原点,以竖直线和垂直于竖直方向的直线为轴建立xoy坐标系,用平滑曲线画平抛轨迹
D测出曲线上某点的坐标x、y,算出小球平抛时的初速度
请写出上述实验步骤的合理顺序:____.
用方框内所给的单词,根据句意用其适当形式填空
comfort buy your be rain least build go fortieth miss
⑴Tomorrow will be my father’s ____ birthday.
⑵Don't go out. It ____ outside now.⑶This sofa is very ____ to sit on.⑷Today is hot. Why not ____ swimming!----That's a good idea.⑸Millie and Simon live in the same____ .⑹Helen often ____ the early bus. So he is often late for school⑺My answers are different from ____ ⑻Outside the garden there ____ a bus stop and many tall buildings.⑼At ____ thirty students go to school by bus in my class.⑽You can ____ a lot of souvenirs here.
小明用显微镜观察洋葱表皮细胞和人口腔上皮细胞作了如下记录,其中正确的是( )
①染色用碘酒是为了更清晰的看到细胞膜②口腔上皮细胞由细胞膜、细胞质、细胞核构成 ③洋葱表皮细胞中有叶绿体④视野中有气泡,可能是盖玻片时操作不当造成的⑤视野中光线过强时应调节成较小的光圈⑥要想看到更多的细胞可以用放大倍数较小的物镜.
看偏旁写字。
口:____ ____ ____
彳:____ ____ ____