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首先,要正确区别机械效率与功的原理。机械效率是有用功在总功中所占的百分比,反映了因机械本身的重力及摩擦的影响时动力功的利用率。功的原理则是指使用机械时人们所做的功都等于不用机械时直接用手所做的功,反映了使用任何机械都不能省功,是在忽略了机械本身的重力和摩擦的情况下,即额外功等于零、机械效率等于1时的一种理想情况。另一方面,在数量上,机械效率中的有用功一般就是
First of all, we must correctly distinguish the principle of mechanical efficiency and work. Mechanical efficiency is the percentage of useful work in the total work, which reflects the utilization of the power when it is affected by the gravity and friction of the machine itself. The principle of work refers to the fact that the work done by people when using machinery is equal to the work done by hand directly when no machinery is used, reflecting that no work can be saved by using any machine. It is under the condition of neglecting the gravity and friction of the machine itself. This is an ideal case when the extra work is equal to zero and the mechanical efficiency is equal to one. On the other hand, in terms of quantity, the useful work in mechanical efficiency is generally