问题 选择题

下列关于力的几种说法,正确的是(  )

A.静止在水平公路上的汽车对路面的压力和路面对汽车的支持力是一对平衡力

B.大小、方向都相同的两个力,作用效果一定相同

C.人推桌子,桌子没有动,是因为推力小于摩擦力

D.游泳时,人向后划水,身体就能往前游,是因为物体间力的作用是相互的

答案

A、静止在水平公路上的汽车对路面的压力和路面对汽车的支持力,大小相等、方向相反、作用在同一条直线上、作用在两个物体上,符合相互作用力的条件,不符合二力平衡条件,故A不正确;

B、力的作用效果不仅与两个力的大小和方向有关,还与作用点有关,故B不正确;

C、人推桌子,桌子没有动处于平衡状态,水平方向受到的推力和摩擦力是一对平衡力,两个力的大小相等,故C不正确;

D、因为物体间力的作用是相互的,所以泳时,人向后划水,身体就能往前游,故D正确.

故选D.

阅读理解

阅读理解。

    Taiwanese singer Stefanie Sun (孙燕姿) looks just like any other young girl. She has short hair, a clear

face and a sweet smile. However, there is something about her that makes her very special: her voice. No

one else can sing like her. Now, Sun is a bright star. She has released many albums (专辑).

     Sun was born in Singapore. When she was a child, her father told her: "A person should always be good

at something in life, so they have something to do for a hobby." Sun chose to learn to play the piano when

she was only five. Then, she took up kick-boxing (搏击操) because she felt she was thin and wanted to

make herself stronger.

     She often sings about the pain and happiness of growing up. The simple but true feelings in her music

are loved by teens. "Sun may be a star, but she seems like a normal girl. She is close to us," said Zhu Liying,

15, a Beijing student. "Her songs give me courage." 

    Eventually, the star was tired because she had worked so hard. She stopped singing for a while and had

a one-year holiday to travel. "I won't give up singing. I just want a rest and to try something new. I hope to

make better music when I come back," Sun said then.

    Now she is working hard again to let her fans hear more beautiful music.

1. Which is NOT true about Sun? [ ]

A. She has short hair.

B. She always has sweet smiles.

C. Her face looks clear.

D. She is a very famous actress.

2. The underlined word "released" in the first paragraph means ______. [ ]

A. made sth. public

B. set free

C. let out

D. made up of

3. Sun learned kick-boxing when she was still a child because ______.[ ]

A. she wanted to be a dancer

B. she wanted to get stronger

C. she enjoyed dancing

D. she wanted to be famous

4. Teenagers love Sun's songs because ______. [ ]

A. her songs are about the pain of growing up

B. she looks clear and is kind to all her fans

C. the feelings in her songs are simple but true

D. her songs are about love and friends

填空题