问题 选择题

2010年11月22日广州亚运会女足决赛开战,日朝两强继小组赛交手后在决赛中会师。双方经过90分钟激战,日本队以1:0战胜朝鲜队摘得金牌。假设某次罚点球直接射门时,球恰好从横粱下边缘踢进,横梁下边缘离地面的高度为h,足球的质量为m,在这过程中,运动员对足球做的功为W1,足球运动过程中克服空气阻力的功为W2,选地面为零势能面,则下列说法正确的是(重力加速度为g)   

A.足球动能的变化量是

B.射门时足球的机械能为

C.足球重力势能的增加量为

D.足球在空中运动的时间为

答案

答案:B

足球动能的变化量等于合外力所做的功为,A错

射门时足球的机械能等于除去重力以外的力对物体做功,B对

足球重力势能的增加量为mgh,C错

因为足球到横梁时竖直速度不为零,所以足球在空中运动的时间小于,D错

单项选择题
阅读理解

Do you know Australia? Australia is the largest island in the world. It is a little smaller than China. It is in the south of the earth. Australia is big, but its population is not large. The population of Australia is nearly as large as that of Shanghai.

The government has made enough laws to fight pollution. The cities in Australia have got little air or water pollution. The sky is blue and the water is clean. You can clearly see fish swimming in the rivers. Plants grow very well.

Last month we visited Perth, the biggest city in Western Australia, and went to a wild flowers’ exhibition. There we saw a large number of wild flowers we had never seen before. We had a wonderful time. Perth is famous for its beautiful wild flowers. In spring every year Perth has the wild flowers’ exhibition. After visiting Perth, we spent the day in the countryside. We sat down and had a rest near a path at the foot of a hill. It was quiet and we enjoyed ourselves. Suddenly we heard bells ringing at the top of the hill. What we saw made us pick up all our things and run back to the car as quickly as we could. There were about three hundred sheep coming towards us down the path.

Australia is famous for its sheep and kangaroos(袋鼠). After a short drive from any town, you will find yourself in the middle of white sheep. Sheep, sheep, everywhere are sheep.

小题1:Australia is _______.

A.the largest country in the world

B.as large as Shanghai

C.not as large as China

D.the largest island in the north of the earth小题2: The government had made _______.

A.too enough laws to fight pollution

B.so many laws that it can fight pollution

C.enough laws that it can hardly fight pollution

D.enough laws because the pollution is very serious小题3: Which of the following is NOT true?

A.Perth is famous for its beautiful wild flowers.

B.Perth is bigger than any other city in Western Australia.

C.Perth lies in the west of Australia.

D.No other city is larger than Perth in Australia.小题4: Which of the following is true?

A.Australia is famous for its sheep, kangaroos and wild flowers.

B.We ran back to the car because we were in the middle of white sheep.

C.Three hundred sheep came towards us because they saw us.

D.If you go to the countryside in Australia, you will see a large number of white sheep.