有关超重和失重，以下说法中正确的是（） A．物体处于超重状_爱下问搜题

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问题选择题

有关超重和失重，以下说法中正确的是（）

A．物体处于超重状态时，所受重力增大，物体处于失重状态时，所受重力减小

B．竖直向上抛出的物体，不计空气阻力，处于完全失重状态

C．在沿竖直方向运动的升降机中出现失重现象时，升降机必定处于下降过程

D．游泳运动员仰卧在水面静止不动时处于失重状态

答案

答案：B

题目分析：重力G=mg，与物体所处的状态无关，A错；失（超）重状态是指物体对支持物的作用力小（大）于自身的重力，物体在空中运动，除了重力，不受任何力，B对，C、D错。

完形填空

If you ask me when I became a mom, I can tell you that the day I became a mom was not the day my daughter was born, but seven years later when I did the best thing I could do for my daughter and myself. I     us from the home that wasn’t really a home at all.
That day, my daughter and I were sitting in our     home having a quiet dinner just as I had always wanted for her. We were talking about what she had done in school and suddenly her little hand     the full glass of milk by her plate. As I watched the white tablecloth and     painted white wall become dark brown, I looked at her small face. It was filled with     , knowing what the outcome of the event would have meant in her father’s     a week before. When I saw that look on her face and looked at the     running down the wall, I simply started     . I am sure she thought I was    , but then she must have realized that I was thinking, “It’s a good thing your     isn’t here!” She started laughing with me, and we laughed until we     . These were tears of joy and     and were the first of many tears that we cried together. That was the day we knew that we were going to be okay.
That was the day I really became a mom. I    that being a mom isn’t only going to ballet, and attending every school concert. It isn’t keeping a(n)     house and preparing perfect meals. It certainly isn’t       thatthings are always normal when they are not. For me, being a mom started when I could laugh over spilt milk.

D．knocked over

问答题简答题

水分对变压器有什么危害？