题目

图中弹簧秤、绳和滑轮的重量均不计,绳与滑轮间的摩擦力不计,物体的重力都是G,在图甲、乙、丙三种情况下,弹簧秤的读数分别是F1、F2、F3,则(                                                        )                                                            A. F3>F1=F2           B.F3=F1>F2    C. F1=F2=F3       D. F1>F2=F3                                                                                                                                   答案:B
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