问题
不定项选择
质量为m的飞机，以速率v在水平面上做半径为r的匀速圆周运动，空气对飞机的作用力的大小等于[ ]
A.
B.
C.
D.
答案
答案：A
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质量为m的飞机，以速率v在水平面上做半径为r的匀速圆周运动，空气对飞机的作用力的大小等于[ ]
A.
B.
C.
D.
答案：A
| 完形填空。 |
| Spring Festival is Chinese New Year's Day. It is in January or 1 . Before Spring Festival, we buy many delicious foods. We buy meat, chicken, 2 , eggs, and vegetables. When Spring Festival 3 , my father, mother, uncle, aunt and I 4 to my grandfather and grandmother's home. We say," 5 New Year!" to each other (互相). We 6 dumplings and 7 TV. We are very 8 . We all like Spring Festival. |
| ( )1. A. December ( )2. A. fish ( )3. A. come ( )4. A. go ( )5. A. Sad ( )6. A. eating ( )7. A. look ( )8. A. hungry | B. November | C. February C. cat C. coming C. going C. Happy C. to eat C. love C. happy | D. March D. cow D. to come D. to go D. Good D. eat D. talk D. sad |