问题 选择题
下列运动过程中机械能守恒的是(  )

A.跳伞运动员打开降落伞在竖直方向向下做匀速直线运动

B.悬点固定的单摆摆球获得一初速后在竖直平面内做圆周运动

C.摩天轮在竖直平面内匀速转动时,舱内的乘客做匀速圆周运动

D.带电小球仅在电场力作用下做加速运动

答案

答案:B

阅读理解

Many of the stories written by Mark Twain take place in Hannibal, Missouri. The small wooden house where he lived as a boy still stands there. Next to the house is a wooden fence. It is the kind described in Twain's book, "The Adventures of Tom Sawyer," published in1876.

In that story, Tom has been told to paint the fence. He does not want to do it. But he acts as if the job is great fun. He tricks other boys into believing this. His trick is so successful that they agree to pay him money to let them finish his work. "The Adventures of Tom Sawyer" is considered one of the best books about an American boy's life in THE the1800s.

Tom Sawyer's good friend is Huckleberry, or "Huck," Finn. Mark Twain tells this boy's story in "The Adventures of Huckleberry Finn." Huck is a poor child, without a mother or home. His father drinks too much alcohol and beats him.

Huck's situation has freed him from the restrictions of society. He explores in the woods and goes fishing. He stays out all night and does not go to school. He smokes tobacco.

Huck runs away from home. He meets Jim, a black man who has escaped from slavery. They travel together on a raft made of wood down the Mississippi River. Huck describes the trip:  "It was lovely to live on the raft. Other places seem so cramped up and smothery, but a raft don't. You feel mighty free and easy and comfortable on a raft... Sometimes we'd have that whole river to ourselves for the longest time... We had the sky up there, all speckled with stars, and we used to lay on our backs and look up at them---. “

小题1:From the second paragraph we learn Tom Sawyer is a ______ boy.

A.kind

B.smart

C.clumsy

D.honest小题2:The reason why Huck runs away from home is that ______.

A.his family is poor

B.he wants to find a friend live with

C.there’s no warn in his home

D.he loves nature and likes to adventure小题3: The underlined word “restrictions” can be replaced by _____.

A.limits

B.prohibition

C.forces

D.rules小题4:Why did Huck feel comfortable living in a raft? Because _____.

A.Huck made the raft by himself

B.Huck could eat fresh food here

C.Huck could have the river there

D.Huck likes to be free小题5:The stories of “The Adventures of Tom Sawyer" and “The Adventures of Huckleberry Finn” are probably _____.

A.completely imaginary

B.according Mark Twain’s experiences

C.Mark Twain’s autobiography(自传)

D.records from his last generation

问答题