问题 选择题

为测出蹦极运动员到达最低点时对弹性绳的拉力大小F1,某同学先记录运动员到达最低点的位置,再用测力装置将弹性绳缓慢拉至该位置,读出测力装置的示数F2,则F1与F2大小相等,建立下列概念时,研究方法与此方法相同的是(  )

A.磁感线

B.瞬时速度

C.电场强度

D.合力与分力

答案

“磁感线”采用假想法、“瞬时速度”采用微元法,而“电场强度”则是比值定义的方法.而“合力与分力”采用等效替代的方法,与题中的等效替代相符.故D正确,A、B、C错误.

故选:D.

阅读理解

.

The UN Environment Programme says that rising temperature could mean the end for some

migrating animals.Migrating or mobile animals move through several environments as they travel away from the cold of winter to warmer areas. Birds may fly from one part of the world to another, perhaps stopping at feeding grounds(聚食场) on the way. Whales and turtles cover vast areas of ocean. The report says that changes in any one of the places which these animals use can cause serious harm."Obviously these animals have developed their traveling patterns over thousands of years. But climate change is almost certain to be extreme over the next 25 t0 50 years, and it is extremely

unlikely that these animals can change their habits fast enough," said the report author Dr. Robert Hepworth.

Hardest hit by rising temperatures are turtles. Scientists have found that at higher temperatures,turtles produce far more female eggs than male ones. In parts of Malaysia, turtle birthing sites are producing only females, the report says, It also provides evidence that some turtles are more likely to develop cancer as the waters get warmer.

With birds, the main problem is climate-related damage to important areas at either end of the travels or at resting places along the way. About one-fifth of migrating birds are now in danger because of climate-related changes including rising sea levels, land loss and more violent storms,the report concludes.Other animals picked out as particularly in danger include:

◆the North Atlantic Right Whale, whose main food( tiny shrimp ) is disturbed by the change in ocean flows

◆the White-beaked Dolphin, which is out-competed by other kinds of dolphins in warmer waters.

The report is not all bad news. Even with major climatic changes, protecting the environment can still help mobile animals to recover.

"We need governments to start taking action at the national and international level. The clock is running." said Dr Hepworth. And some animals are already adapting, with the report mentioning whales that are changing their feeding behavior, finding new feeding grounds and new foods to eat.

48. What does the text mainly talk about?

A. The effect of climate change on migrating animals,

B. How animals are adapting to changes in temperature.

C. The importance of saving migrating animals.

D. The need for government policies to prevent global warming.

49. Which of the following is mentioned as a consequence of rising temperatures?

A. More storms will affect the ability of whales to find their feeding grounds.

B. 20% of all birds are likely to die out because of land loss.

C. Migrating animals can adapt to the changes quickly.

D. Warmer oceans will increase the competition between different kinds of dolphins.

单项选择题