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杠杆是最简单、最基本、最常见的简单机械,也是外形最为多种多样的简单机械．能从实际中辨认出杠杆,需要抓住杠杆的特征,并具有一定的识别能力．一、杠杆的特征从撬石头的撬棒,小孩玩的跷跷板、抽水机的手柄等实例中,可抽象出杠杆的概念:在力的作用下能绕着固定点(支点)转动的硬棒．由杠杆的定义及特征可以看出:“转动”是力的效果,是杠杆的特点．“在力的作用下”是指作用在杠杆上的动力和阻力,是杠杆发生转动的原因．“硬”的含义是指“棒”在受力作用后的转动过程中不变形．“固定点”即支点,是杠杆在转动过程中固定不动的点,是杠杆转动的条件．因此,杠杆必须具有两力——动力(使杠
Leverage is the simplest, most basic, and most common simple machine, and it is the simplest machine with the most varied appearance. Can recognize the lever from the actual, need to grasp the characteristics of the lever, and have a certain ability to identify. First, the characteristics of the lever from the smashing stone smashing rods, children playing sampan, pumping machine handles and other examples, can abstract the concept of leverage: the role of the force can be fixed around the point (pivot) of the hard bar. The definition and characteristics of the lever can be seen: “Rotation” is the effect of force, and it is the characteristic of lever. “Under force” refers to the power and resistance acting on the lever, which is the reason for the rotation of the lever. The meaning of “hard” means that the “stick” does not deform during the rotation after the force. “Fixed point” is the fulcrum, which is the fixed point of the lever during the rotation, and is the condition of the lever rotation. Therefore, the lever must have two forces - power (make the bar