物理中经常涉及到周期性变化的问题,如单缸四冲程汽油机和柴油机的四个冲程为一个周期,我国的交流电频率为50 Hz,周期为0.02 s,电磁波是在空间传播的周期性变化的电磁场.本文以近两年的中考题为例,总结这类题的解法.一、根据已知的周期性变化规律直接求解例1(2010年甘肃兰州)一台单缸四冲程柴油机,飞轮转速为3600转/分,该柴油机活塞1 s对外做____功次.若其效率为 Physics often involves periodic changes in the issue, such as single-cylinder four-stroke gasoline engine and diesel engine four stroke cycle, China’s AC frequency of 50 Hz, a period of 0.02 s, electromagnetic waves are periodically transmitted in space changes Electromagnetic field.This paper summarizes the solution of this kind of questions in the past two years as a case study.According to the known regularity of periodic changes, a single-cylinder four-stroke diesel engine of Example 1 (Lanzhou, Gansu Province, 2010) 3600 r / min, the diesel piston 1 s external ____ times, if its efficiency is