逻辑无环流可逆系统反并联供电的直流电动机,处于逆变状态时作()运行。
A.电动机
B.发电机
C.均衡电抗器
D.逆变变压器
参考答案:B
Read and choose. (阅读理解,选择合适的选项)
Welcome to my school. There are 30 classrooms in my school. Look, this is a big playground.
In this building (大楼), you can see the gym, the library and the art room. They are on the first floor.
There are many story-books and picture books in the library. You can read books in it. My
classroom is on the second floor. It's big and clean. I like it.
1. There are _____ classrooms in my school.
A. thirty
B. thirteen
2. The playground is _____.
A. small
B. big
3. The library is on the _____ floor.
A. first
B. second
4. My classroom is _____.
A. clean
B. small
5. I _____ my school.
A. don't like
B. like
(1)在“研究匀变速直线运动”的实验中:小车拖着纸带的运动情况如图所示,图中A、B、C、D、E为相邻的记数点,相邻的记数点的时间间隔是0.10s,标出的数据单位是cm,则打点计时器在打C点时小车的瞬时速度是______m/s,小车运动的加速度______m/s2.
(2)如图所示为频闪摄影方法拍摄的研究物体做平抛运动规律的照片,图中A、B、C为三个同时由同一点出发的小球.AA′为A球在光滑水平面上以速度v运动的轨迹;BB′为B球以速度v被水平抛出后的运动轨迹;CC′为C球自由下落的运动轨迹.通过分析上述三条轨迹可得出结论:______.