问题 问答题

一物体以v0=20m/s的初速度水平向右作匀减速滑行,1s末速度减为v=16m/s,求:

(1)物体的加速度大小与方向?

(2)3s末的速度是多大?物体在前3s内的位移多大?

(3)8s内的位移多大?

答案

(1)物体的加速度为a=

v-v0
t
=
16-20
1
=-4(m/s2

“-”号表示加速度方向向左

(2)3s末的速度v1=v0+at1=20+(-4)×3=8m/s

物体在前3s内的位移x1=v0t1+

1
2
a
t21
=42m

(3)由v=v0+at可知:t=5s物体已经停止运动

因此,8s内的位移为x=

v0+0
2
t=
20
2
×5
m=50m

答:

(1)物体的加速度大小是4m/s2,方向向左.

(2)3s末的速度是8m/s,物体在前3s内的位移是42m.

(3)8s内的位移是50m.

阅读理解

阅读短文,然后从A、B、C、D四个选项中选出能回答所提问题或完成所给句子的最佳选项。

                                                            Mars Needs Moms!

                                                    ( From: http://en.wikipedia.org)

     Mars Needs Moms! Is an upcoming Disney movie based on the book by Berkeley Breathed. It is set to be

released on March 11,2011 and will be directed by Simon wells and produced by Robert Zemeckis and his studio

Image Movers Digital.

    The movie follows a boy named Milo. Milo is just beginning summer but his mother gives him chores and

tasks like weeding the garden or eating his vegetables. Milo tints (染色) his sister's face purple, but his mother

sees no humor in this. She orders him up to his room. After an argument with his mother in which Milo says "I

don't see what's so special about mothers!" Milo goes to his room. He falls asleep, and does not hear the

rumble (轰隆声) of the rocket landing outside. Martians enter Milo's house and take away his mother. Milo

wakes up and realizes that he has to rescue her . Milo embarks on (开始) an adventure to rescue his mother.

1. What is Mars Needs Moms? [ ]

A. A book.

B. A movie.

C. A garden.

D. A boy.

2. Who is Mars Needs Moms directed by? [ ]

A. Berkeley Breathed.

B. Robert Zemeckis.

C. Simon Wells.

D. Milo.

3. What does the word "Martians" means in Chinese? [ ]

A. 火星人.

B. 地球人.

C. 外国人.

D. 木星人.

4. The information about Mars Needs Moms is provided by ______. [ ]

A. China Daily

B. 21st Century

C. Shanghai Star

D. en.wikipedia

5. Why does Milo begin his adventure? [ ]

A. To wake up his mother.

B. To save his mother.

C. To have a look at Martians.

D. To rescue Martians.

单项选择题