4/8 #1. Since

Yesterday's question was not even touched ... I would only give out one question today, the other one would be the touched question from previous days ... (so if no one is interested in the questions given by me any more, I would simply shut up :D ... )

Sailing: if you go sailing, sailors will probably tell you that the boat moves fastest when the sail forms a certain angle (not 90 degrees) with the direction of the blowing wing. Howver, when the wind is from right behind (90 degree), the boat is surely not moving the fastest. Why?

所有跟帖： 

• 正交，所以在运动方向上没有分量，对吗？ -kevincerry- ♀ (0 bytes) () 04/08/2004 postreply 09:49:23

• ?? -idiot94- ♀ (0 bytes) () 04/08/2004 postreply 10:23:21

• 流体力学？伯努力原理？帆上拉力与推力的合力最大 -kevincerry- ♀ (88 bytes) () 04/08/2004 postreply 15:31:37

• 回复：流体力学？伯努力原理？帆上拉力与推力的合力最大 -idiot94- ♀ (346 bytes) () 04/08/2004 postreply 15:48:32

• 初等的东西很难解释在船帆背风面为什么形成拉力。 -kevincerry- ♀ (0 bytes) () 04/08/2004 postreply 16:07:23

• 回复：初等的东西很难解释在船帆背风面为什么形成拉力。 -idiot94- ♀ (69 bytes) () 04/08/2004 postreply 16:20:22

• I know that answer exactly -kevincerry- ♀ (45 bytes) () 04/08/2004 postreply 16:31:42

• 回复：4/8 #1. Since -独木桥- ♀ (200 bytes) () 04/08/2004 postreply 17:17:33

• exactly :D -idiot94- ♀ (80 bytes) () 04/08/2004 postreply 17:35:46