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关于力的分解,有这样一道常见的习题:一个恒力F分解成两个分力,其中一个分力F_1的方向与F成θ(θ〈90°)角已知,求另一个分力F_2的最小值,其解是显然的,当两个分力互相垂直时,F_1有最小值,最小值为F·sinθ.(见图1). 用动态的观点来考察一下图1的矢量三角形:当F_1由零起逐渐增大时,F_2的变化规律是先减小,后增大.
With regard to the decomposition of forces, there is a common problem: a constant force F is decomposed into two components. One of the components F_1 and F is known as the angle θ (θ<90°). Find another component F_2. The minimum value of the solution is obvious. When two components are perpendicular to each other, F_1 has a minimum value and the minimum value is F·sinθ. (see Figure 1). Consider the vector triangle of Figure 1 in a dynamic view: When F_1 gradually increases from zero, the variation of F_2 decreases first and then increases.