问题 问答题 简答题

什么是滑动摩擦力?

答案

参考答案:

两个相互接触的物体,当其接触面间有相对滑动或相对滑动的趋势时,在接触面间就会产生阻碍彼此相对滑动的切向阻力,这个切向阻力称为滑动摩擦力。

阅读理解

What will the future be like? What do you think of it? Here are some answers from some students.

Roy Burns: I think life in the future will be better. Most people in the world will use “green cars” by 2020, so there will be less pollution and people will live to be 200 years old. As for space travel, I would say, we will travel to Mars(火星) and some other stars in about fifty years.

Helen Lester: If we don’t take good care of the earth now, our children and grandchildren will be born into a world with too much pollution. There will be fewer trees and more buildings, because there will be more people.

Kitty Smith: I agree with Helen Lester. Things will be worse. The weather in the future will be much hotter. Human beings will have to look for another planet to live on.

小题1:What are the students doing?

A.They are talking about space travel.

B.They are predicting the future.

C.They are talking about pollution.

D.They are predicting the weather in the future.小题2:How many things does Roy Burns predict?

A.Two

B.Three

C.Five

D.Six小题3:What does Helen Lester think life will be like in the future?

A.People will live much longer.

B.People will have to live on the moon.

C.Everybody will drive a green car.

D.There will be more buildings and fewer trees.小题4:What does the underlined word “planet” mean in Chinese?

A.太空站

B.宇宙

C.星球

D.南极小题5:Why does Kitty Smith think human beings will have to live on another planet?

A.The earth will be too crowded for human beings to live on.

B.There will be too much pollution everywhere.

C.There will be too many people.

D.The earth will be too hot to live on.

单项选择题