问题 选择题

学校的体育课上,同学们在进行篮球训练.运球过程中篮球由地面弹起后向上运动的过程中(若不计空气阻力),下列说法中正确的是(  )

A.篮球受支持力作用,动能增加

B.篮球动能不变,重力势能增加

C.篮球只受重力作用,机械能减少

D.篮球重力势能增加,动能减少

答案

①在篮球弹起的过程中,篮球的速度越来越小,所以动能是减小的,故A、B是错误的;

②篮球的高度增加,重力势能增加,故D事正确的;

③篮球除了受重力外还受地面对它的支持力的作用,另外机械能是守恒的,故C是错误的.

故选D.

阅读理解

Tristan da Cunha, a 38 –square –mile island, is the farthest inhabited island in the world, according to the Guinness Book of Records. It is 1,510 miles southwest of its nearest, St. Helena, and I, 950 miles west of Africa. Discovered by the Portuguese admiral (上将) of the same name in 1506, and settled in 1810, the island belongs to Great Britain and has a population of a few hundred.

Coming in a close second –and often wrongly mentioned as the most distant land –is Easter Island, which lies 1,260 miles east of its nearest neighbor, Pitcairn Island, and 2,300 miles west of South America.

The mountainous 64 –square –mile island was settled around the 5th century,supposedly by people who were lost at sea. They had no connection with the outside world for more than a thousand years, giving them plenty of time to build more than 1,000 huge stone figures, called moai, for which the island is most famous.

On Easter Sunday, 1722, however, settlers from Holland moved in and gave the island its name. Today, 2,000 people live on the Chilean territory (智利领土). They share one street, a small airport, and a few hours of television per day.

小题1:It can be learned from the text that the island of Tristan da Cunha ________.

A.was named after its discoverer

B.got its name from Holland settlers

C.was named by the British government

D.got its name from the Guinness Book of Records小题2:Which of the following is most famous for moai?

A.Tristan da Cuha.

B.Pitcairn Island.

C.Easter Island.

D.St. Helena.小题3:Which country does Easter Island belong to?

A.Britain.

B.Holland.

C.Portugal.

D.Chile.

单项选择题