问题 填空题

重5牛的物体,受到10牛的水平力作用后,紧帖在竖直的墙面上静止不动,此时物体对墙面的压力为______牛,物体受到的摩擦力为______牛.

答案

物体紧帖在竖直的墙面上静止不动,受到平衡力的作用;在水平方向上,压力和支持力是一对平衡力;物体对墙的压力等于手对物体的水平作用力,即F=10N;在竖直方向上,重力和静摩擦力是一对平衡力;故f=G=5N;

故答案为:10;5.

阅读理解

阅读理解。

根据短文内容,完成下面的句子,每空一词。

     There are few families in the United States that do not have either a radio or television set. Both of them

have become a necessary part of our daily life, keeping us filled with the news of the day, teaching us in many

fields of interest, and making us happy with singing, dancing and acting.

      Marconi, the Italian inventor, who gave us the radio, probably didn't know how much his great invention

would have done for the world in the years to come. Radio had perhaps done as much as any other

communication tool. Things of the world can be reported to people everywhere a few seconds after they

happened. Travelers in out-of-the-way places, ships at sea and even astronauts traveling round the earth are

able to keep in touch with each other by radio.

      Television is another important invention. It lets us see as well as hear the actor. Since its appearance, TV

has done a great deal in the daily life of people everywhere. Many programs are now televised (播放) in color.

     Perhaps the most modem invention is "Telstar", a "star" moving round the earth. It makes it possible for the

people all over the world to be closer than ever before. Now a family in Chicago can watch on TV a motor-car

race in Italy, a table tennis competition in Beijing or a volleyball match in Japan when these events are actually

happening!

1. We can know from the passage that a of families in America have radios or television sets.

2. Radio and TV have become a ______ part of our daily life because they have _____ nearly everything in

    our life.

3. When the writer introduces Marconi in the second paragraph, he means his ______ has much for the world.

4. Since television ,it has made a great-_______ to our daily life.

5. According to the passage"Telstar" is used to help _____ radio or TV information to the people _____ the

   world.

单项选择题