问题 单项选择题

物体同时受到同一平面内的三个力作用,下列几组力中,它们的合力不可能为零的是()

A.5N、7N、8N

B.2N、3N、5N

C.1N、5N、10N

D.1N、10N、10N

答案

参考答案:C

解析:

三个力的合力为零时,则第三个力肯定在第一二两个力的合力范围里,由此判断选项即可.

三个力合力为0时,则任意两个力的合力与第三个力大小相等,方向相反,由此可知,任意一个力在另外两个力的合力范围.

A、5N和7N的合力范围为:2N-9N,8N在合力范围里,故三个力的合力可能为0;

B、2N和3N的合力范围为:2N-5N,5N在合力范围里,故三个力的合力可能为0;

C、1N和5N的合力范围为:4N-5N,10N不在合力范围里,故三个力的合力不可能为0;

D、1N和10N的合力范围为:9N-11N,10N在合力的范围里,故三个力的合力可能为0.

故选C.

阅读理解

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单项选择题