求变力做功问题,即使在高中也是学生学习、教师教学的难点.在初中竞赛、学校自主招生甚至中考中也出现了此类问题,结合具体的试题介绍三种用初中知识求解变化做功大小的方法.通过分析、讨论变力做功的问题,培养学生思维的深刻性、灵活性、独创性及对科学方法的运用能力. In the middle school competition, school self-enrollment and even in the middle school entrance examinations also appeared in such problems, combined with specific test questions introduced three kinds of junior high school knowledge to change the size of the work done Methods By analyzing and discussing the issue of changing the power and doing the work, we should cultivate the profoundness, flexibility, originality and ability of the students to apply scientific methods.