某同学用一校零弹簧测力计测量拉力时，误将物体挂在了拉环上，如_爱下问搜题

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问题选择题

某同学用一校零弹簧测力计测量拉力时，误将物体挂在了拉环上，如图所示，当指针静止时，弹簧测力计的示数是5.0N，则该物重【】

A．一定等于5.0N

B．一定大于5.0N

C．一定小于5.0N

D．一定不小于5.0N

答案

答案：C

如图所示，当物体挂在拉环上时，手对秤钩的拉力等于物体和测力计的重力之和，即测力计的示数F=G物+G秤，所以G物=F-G秤，故物重小于测力计的示数．

故选C

实验题

实验探究：蜡烛刚熄灭时产生的白烟是什么？

提问：蜡烛刚熄灭时，总会有一缕白烟冒出，它的成分是什么呢？

我提出如下假设：

A 白烟是燃烧形成的二氧化碳

B 白烟是燃烧形成的水蒸气

C 白烟是石蜡蒸汽凝成的石蜡固体实验

①吹灭蜡烛，立即用一个沾有澄清石灰水的烧杯罩住白烟，其目的是为了验证假设 _________ 。

②吹灭蜡烛，立即用干冷的玻璃片放在白烟上，玻片没有出现水雾，说明白烟不是 ________ 。

③吹灭蜡烛，立即用燃烧的木条去点白烟，发现蜡烛被重新点燃，说明白烟具有可燃性，这为假设 ______ 提供了依据，同时又排除了假设 _______ 原因是 _____________ 。

完形填空

My father was in the navy, which meant that my mother was married to both my father and the sea. As was often the __1__, we had to pack our belongings into boxes and __ 2__ those we had grown to love. We would arrive at our new home and find ourselves once again __3__ at the pier（码头）waving good-bye to my father as his ship pulled him away from us. My mother would turn my brother and me around before the ship was out of __4__, wipe our tears, and take us back home to start the process of __5__ in the new environment again.
Throughout the years of changing __6__, schools and friends, there remained one constant in my childhood — my mother. For both my __7_ and me, she was the cook, maid and teacher. She played these roles while __8__ some type of part-time job. Leaving a promising career is just one of the __9__ which my mother made for my family as we moved around the world with our father every three years or so. __10__ she had to deal with only a small budget, my mother __11__ managed to make each house the very home that is safe and __12__.
This probably sounds like a depressing way to live, __13__ with two small children: “single” parenthood, short-term friendships, and the inability to __14__ a career or establish a home. But it was not for my mother. She turned this __15__ into adventure for us all! Each relocation was a chance to __16__ another part of the world. My mother __17__ each new culture, climate and neighborhood. Each new house was a __18__ to rearrange furniture, make curtains and hang pictures. Every part-time job was an opportunity to learn something new and work with interesting people.
No matter how difficult the life was, she was always having a __19__ attitude. She always had strength in the face of struggle and change. My mother was so __20__all those years of my childhood — she was my island in a sea of change. She is my hero.

A．leave behind

C．contributions

D．cooperations

B．comfortable

D．opportunity

A．experienced