2015年各地中考试卷,广泛地涉及到效率问题,效率作为中考的一个重点内容,为帮助大家认识和解决好效率问题,现试将“效率问题”归类并进行剖析.一、机械效率如利用机械(杠杆、滑轮、滑轮组、斜面)将物体升高到一定的高度,此时,机械对重物所做的功为有用功,即W_有用=Gh,动力对机械所做的功是总功,即W_总,总功一般有两种表达形式,一种为W_总 2015 around the examination papers, widely related to efficiency issues, efficiency as a key content of the examination, to help you understand and solve the problem of efficiency, the “efficiency problems” are now classified and analyzed. A mechanical efficiency Such as the use of machinery (levers, pulleys, pulleys, bevels) will be elevated to a certain height objects, at this time, the mechanical work done on the heavy work is useful work, that W_ useful = Gh, the power of mechanical work done Is the total work, namely W_ total, the total work generally has two kinds of expressions, one kind is W_ total