问题
选择题
| He didn't pass the exam. He regretted ____ harder. |
A. not having worked B. having not worked C. to have not worked D. not to work |
答案
答案：A
搜题请搜索小程序“爱下问搜题”
| He didn't pass the exam. He regretted ____ harder. |
A. not having worked B. having not worked C. to have not worked D. not to work |
答案：A
，式中S为翅膀的面积，v为小鸟飞行的速度，k为比例系数。如果一小鸟质量为120 g、翅膀面积为
，其水平匀速滑翔的最小速度为12 m/s。设飞机飞行时获得向上的升力与小鸟飞行时获得的升力有同样的规律。现有一架质量为3 200 kg的飞机，它在跑道上加速时获得的最大加速度为5
，若飞机机翼面积为小鸟翅膀面积的600倍，则此飞机起飞的跑道至少要（ ）
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