问题 选择题

如图,在μ=0.1的水平面上向右运动的物体,质量为20 kg.在运动过程中,还受到一个水平向左的大小为10N的拉力F作用,则物体受到的摩擦力为(g=10N/kg)

A.10N,向右

B.10N,向左

C.20N,向右

D.20N,向左

答案

答案:D

题目分析:物体向右运动,受到的摩擦力时地面给的滑动摩擦力,在水平面上,物体对水平面的压力大小等于物体的重力,故根据公式可得,方向与其相对地面的运动方向相反,即向左,故D正确。

阅读理解

阅读理解。

     My father works for the Coca-Cola Company, and as a result of that, I am always changing schools to go

to new places for his job. Right before I moved to California, I had lived in Ohio for six years. I had many

close friends, and it was very hard for me to be able to leave them. When I first moved, my friends and I

talked all the time.

     Then I noticed I started to call my friends less and less each week as I had begun to make friends out here

in California. It came to the point where I never called any of my friends from Ohio anymore, because I felt

that I did not need to talk to them anymore.

     After one of my friends from Ohio called me and told me not to forget who my real friends were, I realized

that I had become a completely (完全地 ) different person. I had adapted (适应) to the new "California" ways

and completely left all of my friends who really cared about me in Ohio behind out of my life. They were the

friends that always cared for me and were there when I needed them the most and I almost let that slip away

(溜走 ).

     As soon as I realized my huge mistake, I started to make more and more calls to my friends from Ohio to

try to keep our friendships.

1. The author moved from Ohio to Califomia _____.

A. to make more friends

B. to start a new life

C. for his father's work

D. for his own study

2. The author's attitude towards friendship changed ______.

A. before he left his friends in Ohio

B. as soon as he arrived in California

C. after he made more calls to his friends in Ohio

D. after he received a friend's call from Ohio

3. What do the underlined words in the last paragraph refer to?

A. The author forgot his old friends in Ohio.

B. The author quarreled with his friends in Ohio.

C. The author disliked his friends in California.

D. The author made too many friends in California.

4. Which sentence shows the main idea of the passage?

A. A friend in need is a friend indeed.

B. Make new friends, but keep the old.

C. Books and friends should be few but good.

D. When in Rome, do as the Romans do.

单项选择题 A3/A4型题