问题 选择题

同一辆汽车以同样大小的速率先后开上平直的桥、凹形桥和凸形桥,在桥的中央处有(  )

A.车对三种桥面的压力一样大

B.车对平直桥面的压力最大

C.车对凹形桥面的压力最大

D.车对凸形桥面的压力最大

答案

平直路面上行驶时,N=mg,在凹形桥的中央,有:N-mg=m

v2
R
,则N>mg.在凸形桥的中央,有:mg-N=m
v2
R
,则N<mg.知在对凹形桥桥面压力最大,对凸形桥桥面压力最小.故C正确,A、B、D错误.

故选C.

阅读理解

阅读理解。

     DICKY lives a poor life with his father. One day his father finds him a strange toy from a junkyard.

Dicky names it Changjiang 7 (CJ7长江七号). CJ7 turns out to be an alien dog with superpowers. Dicky

takes CJ7 to school to help him against bad students.   

      This is the story of CJ7, a popular movie of 2008. Xu Jiao, an 11-year-old girl, plays Dicky. On April

21, Xu won Best New Performer (最佳新人奖) at the Hong Kong Film Awards for her role in CJ7.   

      Xu once said it was difficult to play a boy. "To get a sense of what a boy is like," she said, "I studied

with and watched other boys and played with them a lot."   

About Xu:   

Name: Xu Jiao   

Birthday: August 5, 1997   

Birth place: Ningbo, Zhejiang   

Star sign: Leo (狮子座)

1. DICKY lives a ______ life with his father.   

A. happy     

B. rich     

C. poor     

D. simple

2. Where does Dicky's father find a strange toy that he names Changjiang 7?   

A. in his house 

B. at school  

C. in the park 

D. in a junkyard

3. Dicky takes CJ7 to school to ______.   

A. help him against bad students.

B. help him fight with other students   

C. help him get good grades

D. help him save his father

4. To get a sense of what a boy is like, Xu Jiao ______.   

A. studied with boys   

B. watched other boys 

C. played with boys   

D. All the above.

5. Where was Xu Jiao born?   

A. Hong Kong   

B. Ningbo, Zhejiang 

C. Shanghai   

D. Lianyungang, Jiangsu

判断题