某人骑自行车以10 m/s的速度在大风中向东行驶，他感到风正以同样大小的速率从北方吹来，实际上风的速度是( )．
A．14 m/s，方向为北偏西45°
B．14 m/s，方向为南偏西45°
C．10 m/s，方向为正北
D．10 m/s，方向为正南
答案：A
如右图所示，人的速度为v人，风的速度为v风，在人的行驶方向上感觉不到风，说明风在人的行驶方向上与人同速，仅感觉到从北方吹来的风，则v人＝v风sin θ，v＝v风 cos θ，tan θ＝
＝1，θ＝45°，v风＝
v人＝14 m/s.
| 任务型阅读。维尼看到了这样两张海报，根据下面的海报，回答问题。 | ||||||||||||||
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| 1. Where is Hongshan Zoo? ______________________________________ 2. Can children go to Hongshan Zoo on Sundays? ______________________________________ 3. Amy is 14 and she has ￥50. How many tickets to the zoo can she get? ______________________________________ 4. Why can't Lily go to Nanjing Museum on Monday? ______________________________________ 5. Lucy and Lily both have 10 yuan, which place can they visit? ______________________________________ |