题一艘帆船,扬帆在河中顺风而行,当船航行的速度为多大时,风力对船做功的功率最大? 错解设风速为ν0,船航速为ν,则空气冲击帆面的速度为ν0-ν,空气流对帆面的冲击可看作弹性碰撞,碰撞前后空气流的速度变化为2(ν0—ν).设在时间t内冲击帆面的空气质量为m,对帆面的冲击力为F,由动量定理得 Say a sailing boat, sail in the river, when the speed of the ship is sailing, the wind power to the ship to do the most power? The wrong solution to set the wind speed is ν0, the speed of the ship is ν, then the speed of air impact sail surface is ν0 - ν, the impact of the air flow on the sail surface can be considered as elastic collision. The velocity change of the air flow before and after the collision is 2 (ν0 - ν). The air mass impacting the sail surface within the time t is m, and the impact on the sail surface is Force F, obtained from the momentum theorem