汽车的质量为M，以速率v沿半径为R的拱形桥面行驶，若欲使汽车过_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

汽车的质量为M，以速率v沿半径为R的拱形桥面行驶，若欲使汽车过桥的中心时对桥面的压力正好为零，汽车的速度应为（　　）

A．

g

R

B．

gR

C．

R

g

D．gR

答案

汽车对桥面压力正好为零，有：mg=m

v2

R

，解得；v=

gR

．故B正确，A、C、D错误．

故选：B．

改错题

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。

Last week I went to the concert with my classmates. We got seating
at the end of the row because of we failed to make our reservations.
But we still listened good. The theme of the concert was "Human and
Peace". It was great success. The four-hour concert was not only "good
value", or also "good rocking". The audience were carried away
by the performance. They didn`t applaud enthusiastically after the
conductor and the orchestra rose up and took a bow. The orchestra
really made a hit throughout their dedication. They performed and
recorded most of the classical pieces. It has reported that they
have released many albums and people enjoyed their music.

1. _____
2. _____
3. _____
4. _____
5. _____
6. _____
7. _____
8. _____
9. _____
10. _____

单项选择题

饲料中水分和其他挥发性物质含量的测定方法不适用于（）的测定。

A、奶制品

B、玉米

C、油料籽实

D、A、B、C均不适用