题干

下列金属在一定条件下能够与水反应,且生成金属氧化物的是( )

A:K

B:Mg

C:Fe

D:Cu

上一题 下一题 0.0难度 选择题 更新时间:2019-06-10 01:08:35

答案(点此获取答案解析)

C

同类题4

小明的爸爸新买了一辆小汽车,如图所示,小明坐着这辆汽车匀速行驶144 km,用时2h,消耗汽油9kg,其发动机的功率为23kW.请运用所学的知识解答下列问题.(汽油的热值为4.6×107J/kg)

(1)汽车“发动机”通常都是以汽油或柴油为燃料的,汽油、柴油都属于____ (可再生/不可再生)能源;汽车“发动机”一般需要用水来作冷却剂,这是利用了水的____ 的属性;

(2)汽车在高度行驶过程中发生碰撞,车身停止运动,而乘员由于具有____ 会继续向前运动,此时弹性很强的安全带被拉伸而获得____ 能;安全带做得宽大的目的是____ 

(3)汽车在高度行驶过程中一旦发生碰撞,车身停止,而乘员则会继续向前与车身撞击,甚至能把挡风玻璃撞碎而飞出车外.在发生交通事故时,安全带能对人体起到缓冲的作用,防止出现二次伤害.在发生严重撞击时,方向盘等处的车载气囊会自动充气弹出,在人体接触到安全气囊时,安全气囊通过气囊表面的气孔开始排气,从而起到缓冲作用,减轻身体所受冲击力,大大减小伤害.

对于短文中提到的“缓冲”,文静同学提出了自己的猜想:安全带和安全气囊增加人与碰撞物间的接触时间,从而大大减小撞击力.物理兴趣小组的同学共同设计了如下实验方案:在两个相同的玻璃槽中堆放不同厚度的面粉,从相同的高度先后落下同一只鸡蛋.落在面粉厚度大的槽中,留下较深的坑,鸡蛋完好无损;落在面粉厚度较小槽中,鸡蛋破裂.实验中通过比较____ 来比较撞击时间的长短,根据实验可以验证文静同学的猜想是____ (正确/错误)的;请列举上述“缓冲”物理知识在生活中应用的一个实例:____ 

同类题5

    For years I wanted a garden.I'd spend hours thinking of different things I could plant that would look nice together.
But then we had Matthew, and Marvin, and the twins Alisa and Alan, and then Helen.I was too busy raising them to grow a garden.
Money was not enough.Neither was time.Often when my children were little, one of them would want something that cost too much, and I'd have to say, “Do you see a money tree outside? Money doesn't grow on trees, you know.”
    Finally, all the children got through high school and college and were off on their own.I started thinking again about a garden.
Then, one spring morning, on Mother’s Day, I was working in my kitchen.Suddenly, I looked out of the window and there was a new tree, planted right in my yard.There were things blowing around on it.Then I put my glasses on—and I couldn't believe what I saw.There was a money tree in my yard!
    I went outside to look.It was true! There were dollar bills(帐单), one hundred of them, hanging all over that tree.There was also a note among them, “Thank you for your time, Mom.We love you!”
    Later, my children bought me tools, ornaments, a sunflower stepping stone and gardening books.A new page started in my life.
That was three years ago.My garden's now very pretty, just like I wanted.When I go out and take care of my flowers, I don’t seem to miss my children as much as I once did.It feels like they're right there with me.Now every year when winter comes, I look out of my window and think of the flowers I'll see next spring in my little garden.I think about what my children did for me, and I get tears in my eyes—every time.
I'm still not sure that money grows on trees.But I know love does!