题目

如图所示，A、B两球用劲度系数为k1的轻弹簧相连，B球用长为L的细绳悬于0点，A球固定在0点正下方，且O、A间的距离恰为L，此时绳子所受的拉力为F1，现把A、B间的弹簧换成劲度系数为k2的轻弹簧，仍使系统平衡，此时绳子所受的拉力为F2，则F1与F2大小之间的关系为（     ）                                                                                                                                                              　   A． F1＜F2        B． F1＞F2       C．F1=F2       D． 无法确定                                                                                                                                     答案：C

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