问题 选择题

忽略空气阻力,抛出后的小球在空中运动轨迹如图所示,抛出后的小球

A.受到惯性力的作用,继续向前运动

B.受到重力作用,运动状态发生改变

C.不受力,机械能不变

D.上升过程重力势能转化为动能

答案

答案:B

小球出手之前,和手一起运动,抛出的小球,不再受到手的推力,由于惯性保持原来的运动状态,继续前进.小球出手前后都受到重力作用,重力改变了小球的运动方向和速度,运动状态不断发生改变.故选B.

阅读理解

To us it seems so natural to put up an umbrella to keep the water off when it rains, But actually the umbrella was not invented as protection against the rain, Its first use was as a shade against the sun!

Nobody knows who first invented it, but the umbrella was used in very ancient times . Probably the first to use it were the Chinese in the 11th century B C.

We know that the umbrella was used in ancient Egypt and Babylon as a sunshade. And there was a strange thing connected with its use: it became a symbol of honor. In the Far East in ancient times, the umbrella was allowed to be used only by those in high office.

In Europe, the Greeks were the first to use the umbrella as a sunshade. And the umbrella was in commonly used in ancient Greece. But it is believed that the first persons in Europe to use the umbrella as protection against the rain were the ancient Romans.

During the Middle Ages, the use of the umbrella practically disappeared. Then it appeared again in Italy in the late sixteenth century. And again it was considered as a symbol of power. By 1680, the umbrella appeared in France and later in England.

By the eighteenth century, the umbrella was used against rain throughout most of Europe.

Umbrellas have hot changed much in style during all this time, though they have become much lighter in weight. It wasn’t until the twentieth century that women’s umbrellas began to be made , in a whole variety of colors.

小题1:According to this passage, the umbrella was probably first invented in ancient_______.

A.China

B.Egypt

C.Greece

D.Rome小题2:Which of the following statements is not true about the umbrella?

A.No one exactly knows who the inventor of the umbrella was

B.The umbrella was first invented to be used as protection against the sun.

C.The umbrella changed much in style in the eighteenth century

D.In Europe, the Greeks were the first to use the umbrella as a sunshade.小题3:A strange feature of the umbrella’s use is that it was used as__________.

A.protection against rain

B.a shade against the sun

C.a symbol of honor and power

D.women’s decoration (装饰)小题4:In Europe, the umbrella was first used against the rain_______________.

A.during the Middle Ages

B.by the 18th

C.in Rome

D.in Greece小题5:This passage talks mainly about_______________.

A.when and how the umbrella was invented

B.why the umbrella was so popular in Europe

C.the development of the umbrella

D.The history and use of the umbrella

单项选择题