题目

如图所示，两个共点力F1、F2的大小一定，夹角θ是变化的，合力为F．在θ角从0逐渐增大到180°的过程中，合力F的大小变化情况（                                                                                          ）                                                                                                              　   A． 从最小逐渐增加                   B． 从最大逐渐减小到零 　   C． 从最大逐渐减小                   D．       先增大后减小                                                                                                                                答案：C

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