问题 选择题

随着世界航空事业的发展,深太空探测已逐渐成为各国关注的热点.假设深太空中有一颗外星球,质量是地球质量的2倍,半径是地球半径的l/2.则下述判断正确的有(  )

A.在地面上所受重力为G的物体,在该外星球表面上所受重力变为2G

B.该外星球上第一宇宙速度是地球上第一宇宙速度的2倍

C.该外星球的同步卫星周期一定小于地球同步卫星周期

D.该外星球上从某高处自由落地时间是地面上同一高处自由落地时间的一半

答案

A、根据G=

G0Mm
R2
G′=
G02Mm
(
1
2
R)2
=8G
故A错误;

B:万有引力提供向心力,得:G=

mv2
R
,所以:v=
GR
m
v′=
8G?
1
2
R
m
=
4GR
m
=2v
.故B正确;

C:不知道外星球的自转周期,所以无法比较该外星球的同步卫星周期与地球同步卫星周期关系,故C错误;

D:某高处自由落地时间:t=

2h
g
=
2h
G
m
=
2mh
G
t′=
2mh
8G
=
1
8
t
.故D错误.

故选:B

选择题
阅读理解

Restaurant owners should not use disposable chopsticks for the good of their health and the environment , an official of the China Cuisine Association(中国烹饪协会)said.

Bian Jiang, its secretary general, recently called on restaurant owners to say no to one-off tableware(餐具), especially wooden chopsticks. “The country produces and throws away over 45 billion pairs of wooden chopsticks every year, at a cost to the environment of about 25 million tree.” Bian said.

“That’s a heavy blow to the county’s shrinking(正在减少的) forests,” he said, “We should not turn a deaf ear to the call for environmental protection. We should stop using disposable tableware from now on.”

In order to discourage the use of wooden chopsticks and to protect wooden resources, the government put a 5% tax on them in April.

The use of disposable chopsticks has been discussed for years. Their supporters say that both restaurant owners and consumers prefer them, and that an industry has grown up around their production.

. 小题1:

The secretary general suggests that wooden chopsticks be stopped from being used because           .

A.they cause a lot of pollution of the environment

B.the environment is no longer green

C.the government is not happy with that

D.too many trees are cut小题2:

From the text we know that the idea of no disposable tableware will be           .

A.hard to put into practice

B.welcomed by a lot of people

C.receiving indifferent attitudes

D.rejected by some people小题3:

What does the underlined word “disposable” in the first paragraph mean?

A.Waste

B.Expensive

C.Man

D.One-use小题4:

What’s the main idea of the text?

A.Many people support the idea of saying no to using wooden chopsticks.

B.The government calls on people to stop using wooden chopsticks.

C.Disposable tableware wastes a lot of forests and does damage to the

environment.

D.People are aware of the cost of using disposable tableware