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如图1所示,某人站在岸上通过绕过定滑轮的绳子向岸边拉船,他拉绳子的速率υ不变,当拉船的绳子与水平面成θ角时,船前进的速度 u 有多大?一、常规解法分析在这里讨论的是船运动的速度问题,以船与绳子的连接点为研究对象,它的实际运动速度 u 的方向水平向左,这就是合速度.船的运动可以认为是两个运动的合成:一个是沿绳子方向向上的运动,速度大小即为υ;另一个分速度的方向垂直于绳,如图2所示,作出速度矢量的平
As shown in Figure 1, a person standing on the shore pulls the boat through the ropes that pass the fixed pulley. He pulls the rope at a constant rate, and when the rope of the pulling boat makes an angle θ with the horizontal plane, the speed of the boat advances. How big? First, the conventional solution analysis is discussed here is the speed of the ship’s movement, the connection point of the ship and the rope as the object of study, its actual movement speed u direction horizontally to the left, this is the combined speed. The ship’s movement It can be considered as the synthesis of two movements: one is the upward movement in the direction of the rope, and the speed is the size; the other direction of the speed is perpendicular to the rope, as shown in FIG. 2 , and the speed vector is made flat.