2013年上海高考物理试卷第20题,在考试院公布答案后,受到众多教师的热议和争论,许多中学物理教师甚至大学教师,纷纷在一些物理教学刊物上发表文章进行探讨、释疑、剖析等.至今仍有好多中学物理教师在相关物理教学QQ群中激烈讨论,其焦点是选项(C)和(D)到底哪个正确,虽然有许多文章赞同考试院公布的结果(B)、(C).但对(C)选项的论述情况也并不令人满意,总存在着隐隐的不解.为了便于说明下面先给出原题及考 2013 Shanghai college entrance examination physical examination paper 20 questions, published the examination in the examination room after many teachers hot debate and controversy, many secondary school physics teachers and even university teachers, have published articles in some physics teaching journals to explore, explain, analysis, etc. There are still a lot of secondary school physics teachers in the relevant physics teaching QQ group heated discussion, the focus is option (C) and (D) in the end which is correct, although there are many articles agree with the examination results announced by the hospital (B), (C) .But the discussion on the (C) option is not satisfactory, there is always a faint puzzled .In order to facilitate the explanation given below the original title and test