问题 选择题

下列生活中物体的运动:①在笔直公路上行驶的汽车;②摆动的时钟钟摆;③随风飘动的旗帜;④摇动的大绳;⑤汽车前玻璃的雨刷的运动;⑥从楼顶自由落下的球.属于平移的个数为(  )

A.1个

B.2个

C.3个

D.4个

答案

①笔直公路上行驶的汽车,其形状、大小没有改变,各点运动的方向、距离相同,故本项属于平移;

②摆动的时钟钟摆,其形状、大小没有改变,但移动方向改变,故本项不属于平移;

③随风飘动的旗帜,其形状发生改变,故本项不属于平移;

④摇动的大绳,其形状发生改变,故本项不属于平移;

⑤汽车前玻璃的雨刷的运动,其形状、大小没有改变,但移动方向改变,各个点的运动距离不一样,本项不属于平移;

⑥从楼顶自由落下的球,其形状、大小没有改变,所有点移动的方向、距离一致,故本项属于平移;

所以,属于平移的个数为2.

故选B.

阅读理解

阅读理解。

     Every time you turn on the television or take a ride in a car,you could be adding to a problem called acid

rain (酸雨). In this article, you'll learn how acid is created, and how it affects us, and more importantly, what

we all can do to prevent it. 

How is acid rain created?

     When people use fuels (燃料), such as coal and gasoline, poisonous gases are give off. When these gases

mix with rain, acid rain forms. Many power stations burn fuels in order to creat the electricity (电) that we

use in our homes and offices every day. Cars and trucks also send these gases into the air when they burn

gasoline.When rain mixes with these gases, harmful things called acids form. This is acid rain.

How does acid rain affect us?

     Acid rain damages (毁坏) everything that it touches. It poisons our rivers, ponds, lakes, and oceans along

with all the life in them. It pollutes our soil and crops, harms trees, and can even kill fish and plants. Acid rain

also eats away at buildings.

How can we prevent acid rain?

     We need to cut down on the pollution that gets into our air. Turn off lights, television, and other electrical

appliances if you are not using them, Walk or take a bike whenever possible. If you are travelling a long

distance, take a bus or train to save fuel.

     As research shows, acid rain harms our environment. But people everywhere can take small steps now to

help protect our environment for future generations.

1. When power stations burn fuel, ______.

A. acid rain form

B. air pollution is caused

C. noise pollution is caused

D. acid rain gets heavier

2. According to the article, acid rain affects us ______.

A. suddenly

B. slightly

C. seriously

D. immediately

3. What advice does the article give us?

A. Go to school on foot or by bike if we can.

B. Go to bed earlier in order to use less electricity.

C. Travel by bus to prevent acid rain.

D. Turn off the television on rainy days.

4. What is the best title of the article?

A. Preventing Acid Rain

B. Forming of Acid Rain

C. Acid rain, Heavy Rain

D. Acid Rain, Killer Rain

判断题