问题 选择题

一质量为1kg的滑块,以4m/s的速度在光滑水平面上向左滑行.从某一时刻起在滑块上作用一水平向右的力,这个水平力作用一段时间后被撤去,已知这个力在此过程中对滑块共做了10J的功,则最后滑块的速度方向和大小分别为(  )

A.方向向左,6m/s

B.方向向左,4m/s

C.方向向右,6m/s

D.方向向右,4m/s

答案

根据动能定理得,WF=

1
2
mv2-
1
2
mv02,解得v=6m/s.因为开始时水平力方向与初速度方向相反,知末速度的方向水平向右.故C正确,A、B、D错误.

故选C.

不定项选择
阅读理解

Do you enjoy reading? Here readers of your age from all over the United States recommend (推荐) great books for you to read:

My favorite book is Don’t Die, My Love by Lurlene McDaniel. I love all her books, but this was the first one I read and I have to say, it is by far my favorite. It doesn’t end like other books, and I cried while reading.

I think Nancy Drew is great! Nancy is a detective (侦探) who has many fantastic ideas! I love it because it’s a book from when my grandma was my age, and I can share the fun with her!

I highly recommend Skinny Bones by Barbara Park. It is funny so please add it on your book list. You don’t want to miss out funny stories!

I would suggest ______ by Judy Blume. It is based on real things that happened to Judy Blume. It is about a girl, Alice, who meets some girls at a new state. They become friends, make a club and meet once a week. They stop after two weeks because they all like a boy in their class and put him as number one. I think every girl should read this because it is about our growing up.

I read a book called Neela: Victory Song and it was so good I read it twice! It takes place in India in 1936 and this 12-year-old girl named Neela tries to save her father! It has lots of history in it! I also learned a lot about different cultures! The author’s name is Chitra Banerjee Divakaruni.

44. According to the reader, Skinny Bones can be described as a ________ story.

A. sad                     B. history                   C. funny                       D. detective

45. From which book can we learn different cultures?

A. Skinny Bones.        B. Nancy Drew.          C. Don’t Die, My Love. D. Neela: Victory Song.

46. The best name of the 4th book is ________.

A. My Secret   B. Growing Trouble   C. Three Friends  D. Alice Learns a Lesson

47. Which is TRUE about Nancy Drew?

A. Both the reader and the reader’s grandma love this book.

B. It’s based on real things that happened to the author.

C. It’s about a12-year-old girl who tries to save her father.

D. It doesn’t have a common ending like other books.