问题 计算题

小明和父母到奶奶家过端午节.细心的小明发现.奶奶家的电水壶和自己家的电水壶是同一品牌的.但是电功率不同,他收集的数据如下表.小明想.烧开同样多的水,哪一个更省电呢?于是他把奶奶家的电水壶拿到了自已家.把两个水壶都装上2.5L的水并烧开。奶奶家的电水壶用了12min.而自已家的用了20min(均在额定电压下工作).

(1)请你通过计算说明.哪个电水壶更省电?并简要分析省电原因.

(2)你在生活中还有哪些节约用电的具体做法?请列举一例

答案

解:

(1)奶奶家的电水壶: t1=12min=720s,W1=P1t1=1200W×720s=86400J=8.64×105J,小明家的电水壶: t2=20min=1200s,W2=P2t2=800W×1200s=9600000J=9.6×105J,W1<W2所以奶奶家的壶更省电

原因:大功率的电水壶加热时间短.升温快.热量损失少.所以节约电能;

(2)不让电视机处于待机状态(或不把空调的温度调的过低、或尽可能减少电冰箱开关门的时间或次数、或不将电视机的音量和亮度调的过大、或做到随手关灯、或将电冰箱放在阴凉通风处等).

阅读理解

SPACE is a lonely place. Hundreds of thousands of kilometers from home, astronauts have a hard life. It stands to reason that, once in a while, they need to have a good cry. But this is a lot harder than it sounds.

We still know very little about space, and about living in zero gravity. In fact, we are discovering new things every time astronauts take to the skies (and beyond). As The Atlantic reported in January, crying is not all that simple in space. This is because when a person normally cries,  gravity makes their tears move downwards. But in a spacecraft, this is not the case. Here, there is no gravity, which is why we so often see pictures of astronauts floating around. This means that, strangely, when you cry your tears have nowhere to go. As a result, they just stick to your eyes.

In May 2011, astronaut Andrew Feustel experienced this. “Tears,” as he said, “don’t fall off your eye… they just kind of stay there. ” This can be quite painful. In space, your eyes get very dry, and the added moisture is irritating (气人的). Sometimes, things get even weirder(更怪异的). The astronaut Ron Parise told The Atlantic that when tears get big enough, they “break free of the eye and float around”.

No one can be quite sure why we cry. Why should water in our eyes have anything to do with feeling sad? If you stop to think about it, crying is a very strange thing indeed. And now, thanks to the wonders of space, it just got even stranger.

小题1:The first paragraph mainly wants to tell us that       .

A.living in space is lonely

B.it’s easy to feel sad in space

C.it’s hard to cry in space

D.nobody wants to live in space小题2:If astronauts cry in spacecraft, their tears will       .

A.move downwards

B.move upwards

C.go out of the window

D.stick to their eyes小题3:Astronauts feel       if tears are always in their eyes.

A.sad

B.comfortable

C.happy

D.uncomfortable小题4:What can we learn from the passage?

A.In space our eyes are very wet.

B.Tears will float around if they are big enough in space.

C.People know everything about living in zero gravity.

D.Gravity makes people’s tears move upwards in space.

单项选择题