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一、用动能定理求某点速度的大小图1例1如图1,小球质量为m,用长为l的轻绳悬挂于天花板上的O点.现用某力拉球,使轻绳转过θ角.求:若用水平恒力F拉动,球由P处到达Q处时,球的末速度大小.分析与解求物体在Q点的速度v.已知物体在P点的速度为零,由P到Q的运动过程中只有重力和外力做功,两个力都是恒力,可直接应用动能
First, with the kinetic energy theorem to find the speed of a certain point Figure 1 Example 1 Figure 1, the mass of the ball m, with a length of l hanging rope hanging on the ceiling of the O point. Turn through angle θ. Seeking: If the horizontal constant force F pull the ball from P to Q at the end of the speed of the ball. Analysis and solution of the object in the Q point velocity v. Known object velocity at the P point Is zero, from P to Q only gravity and external force in the process of doing work, the two forces are constant force, can be directly applied kinetic energy