问题 问答题

如图为中国运动员推出冰壶的镜头,2010年温哥华冬奥会所用冰壶质量是19kg,底面积0.04m2.(g=10N/kg)

(1)冰壶受到的重力是多少N?

(2)冰壶静止在冰面上对冰面的压强为多少Pa?

(3)冰壶被推出后仍向前滑行是因为冰壶具有______;但最后冰壶会停下来,其原因是______.

答案

(1)冰壶受到的重力:

G=mg=19kg×10N/kg=190N;

(2)冰壶静止在冰面上时,对冰面的压力:

F=G=190N,

对冰面的压强:

p=

F
S
=
190N
0.04m2
=4750Pa;

(3)冰壶被推出后,由于惯性,要保持原来的运动状态,仍能向前滑行;

冰壶滑行一段距离后,由于受到地面的摩擦力,使冰壶最终停下来.

答:(1)冰壶受到的重力是190N;

(2)冰壶静止在冰面上对冰面的压强为4750Pa;

(3)惯性;冰壶受到摩擦力的作用.

阅读理解

阅读理解。

     Running like the wind, roaring (咆哮) like thunder, tigers have long been feared and respected as a king

of the animal world. But last week a report said that there are no more than 30 wild tigers left in south China.

     This was the conclusion of a team of scientists from China's State Forestry Administration and the World

Nature Fund.

     The South China tiger, also known as the Chinese tiger, is native to southern China. In the 1950's, there

were over 4000 tigers found in mountain forests in the country. But due to the destruction of their natural

habitat (栖息地) and uncontrolled hunting, it has been pushed on to the list of the world's top ten most

endangered species.  

     Sixty-six of the big cats can be found in the cages of a dozen zoos around China. But they are nothing like

their wild cousins. They have lost their natural skills such as hunting and killing. If they were set free they

could not look after themselves.

     "Breeding has damaged the quality of the species", said Pei Enle, deputy director of the Shanghai Zoo.

     To reintroduce the species into the wild, the country started a programme to send five to ten young tigers

to South Africa. Four of them have already arrived. Progress has been made as two elder tigers have

recovered some of their instincts(本能) and can hunt wild animals by themselves at the African base.

     " South Africans are very experienced in reintroducing big animals to the wild. The country has very good

natural conditions for the tigers to learn in", said Lu Jun, office director of the National Wildlife Research and

Development Center. "We tried in Fujian Province, but it was not successful as there was not a complete

eco-chain (生物链) and there was a lack of space." The tigers should return to China in 2007 when the

reservations in Fujian are ready.

1. What is the main reason for the South China tiger becoming one of the world's top ten most

endangered species?

A. Because it has lost its natural instincts.

B. Because there is not a complete eco-chain.

C. Because there is no space for it.

D. Because uncontrolled hunting has destroyed its natural living conditions.

2. How is the programme of sending several tigers to South Africa getting on?

A. Its effect still remains to be seen.

B. Two tigers can already compete with their wild cousins.

C. Some of the tigers are already on the road to recovering their natural skills.

D. The tigers should be able to recover their instincts completely by 2007.

3. By saying " but they are nothing like their wild cousins", the writer means that ______.

A. they are no longer feared by other wild animals

B. they don't know how to hunt or kill

C. a complete change has resulted in the species because of breeding

D. to reintroduce them into the wild has become an urgent task

4. What is the purpose of sending young tigers to South Africa?

A. To help the tigers recover their ability to live in the wild.

B. To provide them with a better environment.

C. To get the tigers to go on a tour.

D. To find a complete eco-chain for them.

5. Which one is not the reason for South Africa being chosen as the training place?

A. Because the tigers can hunt wild animals by themselves at the African base.

B. Because South Africans are skilled at dealing with the tigers.

C. Because there is a complete eco-chain and enough space there.

D. Because the country has good natural conditions for the tigers to learn in.

单项选择题