在绕地球做匀速圆周运动的飞船上,宇航员可以自由“漂浮”。其原因是宇航员( ) A.不受地球重力的作用 B.受到的地球重力提供向心力 C.受到的地球重力和浮力相抵消 D.受到的地球重力和月球引力相抵消 答案:B 解析:绕地球做匀速圆周运动的飞船宇航员可以自由“漂浮”是由于受到的地球重力全部提供绕地球做匀速圆周运动的向心力。使其处于完全失重状态,因而可以自由“漂浮”,B正确。
短文改错
此题要求改正所给短文中的错误。对标有题号的每一行作出判断;如无错误,在该行右边横线上面一个勾(√);如有错误(每行只有一个错误),则按下列情况改正:
该行多一个词:把多余的词用斜线(\)划掉,在该行右边横线上写出该词,并也用斜线划掉。
该行缺一个词:在缺词处加一个漏字符号(∧),在该行右边横线上写出该加的词。
该行错一个词:在错的词下划一横线,在该行右边横线上写出改正后的词。
注意:原行没有错的不要改。
My classmate Liu Hong is a warm-hearted girl.She is
1.________
good at studying, singing, dancing and playing piano.After
2.________
hear Sichuan earthquake, she felt very sad about it.
3.________
She decided to do something to helping Sichuan people.
4.________
First she calls her friends up and came up with having a
5.________
benefit show.Then she handed out advertisement with her
6.________
friends or put up signs asking people to watch.
7.________
Luckily she did very well.A lot of people moved
8.________
and gave their hands to the Sichuan people.At last, she
9.________
raised5,000yuan.She gave up all the money to the
10.________
quake-hit areas.