In cold, damp weather, the buildup of ice on airplane wings can pose significant aerodynamic problems. Which of the following effects would you expect?A.As ice builds up on the top of the wing, drag increases.B.As ice builds up on the top of the wing, lif

题目

In cold, damp weather, the buildup of ice on airplane wings can pose significant aerodynamic problems. Which of the following effects would you expect?

A.As ice builds up on the top of the wing, drag increases.

B.As ice builds up on the top of the wing, lift increases.

C.As ice builds up on bottom of the wing, lift decreases.

D.All of the above

更多“In cold, damp weather, the buildup of ice on airplane wings can pose significant aerodynamic problems. Which of the following effects would you expect?A.As ice builds up on the top of the wing, drag increases.B.As ice builds up on the top of the wing, lif”相关问题

第1题

资料：A high-precision NASA radar instrument left a NASA airport in Southern California for Iceland on January 28 to create detailed maps of how glaciers move in the dead of winter. This will help scientists around the world better understand some of the most basic processes involved in melting glaciers, which are major contributors to rising sea levels. NASA used the same airborne instrument in June 2012 to map the summer flows of two Icelandic ice caps. The ice caps — large areas of permanent snow and ice cover — encompass multiple glaciers flowing in different directions and at different speeds. By mapping the same ice caps now, in winter, when the surface remains frozen all day, and then comparing the winter and summer velocities, the researchers will be able to isolate the effects of melt water. Above is a view of a small part of the Hofsjkull ice cap, which encompasses several glaciers. The fan at upper left is part of a glacier called Mlaj?kull. For more on the research, see this NASA press release.How can the scientists figure out the effects of melting water?A.By melting the frozen iceberg in winter. B.By observing the snow's moving directions. C.By isolating ice from water in sunlines. D.By comparing the glaciers moving speeds.

点击查看答案
第2题

共用题干 Rainmaking1 The idea of rainmaking is almost as old as man,but it was not until 1946 that man succeeded in making rain.In ancient times,rainmakers had claimed to bring rain by many methods:dancing.singing-Kiiiing animals t including humans).2 For a long time,men have understood where rain comes from.Water from the surface of oceans and lakes becomes part of the air,where it forms clouds from which rain falls.But exactly what starts the formation of raindrops was not known until quite recently.A man named John Aitken proved that drops of water gather around tiny bits of dust or other matter.The centers of the drops are so small that the human eye cannot see them.Without such centers,it seems raindrops do not form.3 During World War Ⅱ,Dr.Irving Langmir,and his assistant Schaefer,were hired by the General Electric Company to study how and why ice forms on the wings of airplanes.They went to a mountain in New Hampshire,where snowstorms are common and cold winds blow.They were surprised to find that often the temperature of the clouds surrounding them was far below the freezing point,and yet ice did not form in the clouds.4 After the War,Schaefer experimented with a machine that created cold,moist air similar to the air found in clouds.To imitate the moist air of a cloud,Schaefer would breathe into the machine.Then he would drop into the freezer a bit of powder,sugar,or some other substance.For weeks and months he tried everything he could imagine.Nothing happened.No crystals of ice were formed.None of the substances would serve as the center of a snow crystal or raindrops.5 One July morning,Schaefer was dropping in bits of various substances and watching the unsuccessful results.Finally,a friend suggested that they go to eat lunch and Schaefer went with him.As usual,he left the cover of the freezer up,since cold air sinks and would not escape from the box.6 Returning from lunch,Schaefer found that the temperature of the freezer had risen to a point higher than that required for ice crystals to remain solid.There were two choices now.He could close the cover and wait for the freezer itself to lower the air temperature,or he could make the process occur faster by adding dry ice-a gas in solid form that is very,very cold.He chose the latter plan.As he dropped the steaming white dry ice into the freezer,he happened to breathe out a large amount of air.And there,before his eyes,it happened!He had made ice crystals,not by adding centers to the moisture,but by cooling the breath so much that the liquid had to form crystals!Then he began to blow his breath into the freezer and drop large pieces of dry ice through it to create crystals which became a tiny snowstorm falling slowly to the floor of his laboratory.7 After planning carefully,Schaefer made an experiment by dropping dry ice from his plane to the clouds below him.As was expected,snow formed and fell from the bottom of the cloud.Schaefer succeeded.He made history.Schaefer found a way of how to make ice crystals______.A:imaginativelyB:recentlyC:carefullyD:unscientifically E:accidentally F:satisfactorily

点击查看答案
第3题

共用题干 Rainmaking1 The idea of rainmaking is almost as old as man,but it was not until 1946 that man succeeded in making rain.In ancient times,rainmakers had claimed to bring rain by many methods:dancing,singing,killing animals(including humans).2 For a long time,men have understood where rain comes from.Water from the surface of oceans and lakes becomes part of the air,where it forms clouds from which rain falls.But exactly what starts the forma- tion of raindrops was not known until quite recently.A man named John Aitken proved that drops of water gather around tiny bits of dust or other matter. The centers of the drops are so small that the human eye can- not see them.Without such centers,it seems raindrops do not form.3 During World War Ⅱ,Dr. Irving Langmir,and his assistant Schaefer,were hired by the General Electric Company to study how and why ice forms on the wings of airplanes.They went to a mountain in New Hampshire,where snowstorms are common and cold winds blow. They were surprised to find that often the temperature of the clouds surrounding them was far below the freezing point,and yet ice did not form in the clouds.4 After the War,Schaefer experimented with a machine that created cold,moist air similar to the air found in clouds.To imitate the moist air of a cloud.Schaefer would breathe into the machine.Then he would drop into the freezer a bit of powder,sugar,or some other substance.For weeks and months he tried everything he could imagine.Nothing happened.No crystals of ice were formed.None of the substances would serve as the center of a snow crystal or raindrops.5 One July morning,Schaefer was dropping in bits of various substances and watching the unsuccessful results.Finally,a friend suggested that they go to eat lunch and Schaefer went with him.As usual,he left the cover of the freezer up,since cold air sinks and would not escape from the box.6 Returning from lunch,Schaefer found that the temperature of the freezer had risen to a point higher than that required for ice crystals to remain solid.There were two choices now.He could close the cover and wait for the freezer itself to lower the air temperature,or he could make the process occur faster by adding dry ice a gas in solid form that is very,very cold.He chose the latter plan.As he dropped the steaming white dry ice into the freezer,he happened to breathe out a large amount of air. And there,before his eyes,it happened ! He had made ice crystals,not by adding centers to the moisture,but by cooling the breath so much that the liquid had to form crystals!Then he began to blow his breath into the freezer and drop large pieces of dry ice through it to create crystals which became a tiny snowstorm falling slowly to the floor of his laboratory.7 After planning carefully,Schaefer made an experiment by dropping dry ice from his plane to the clouds below him.As was expected,snow formed and fell from the bottom of the cloud.Schaefer succeeded. He made history.Schaefer found a way of how to make ice crystals_________.A:imaginativelyB:recentlyC:carefullyD:unscientificallyE:accidentallyF:satisfactorily

点击查看答案
第4题

共用题干第一篇Arctic MeltEarth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice in the Arctic Ocean（北冰洋）fell to a record low.Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the summer. But for many years,the amount of ice left by the end of summer has been declining.Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and 2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago. This continuing trend has made scientists concerned.There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous record high.With both air and water getting warmer,the ice is melting from both above and below. In some parts of the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning of the summer measured just 50 centimeters by season's end.The new measurements suggest that melting is far more severe than scientists have seen by just looking at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Researchand Engineering Laboratory in Hanover,N.H.Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.By the end of summer 2007 the ice cover in the Arctic was ________.A:4.2 million square kilometersB:11.4 million square kilometersC:1.13 million square kilometers D:38 million square kilometers

点击查看答案
第5题

共用题干第一篇Arctic MeltEarth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice in the Arctic Ocean（北冰洋）fell to a record low.Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the summer. But for many years,the amount of ice left by the end of summer has been declining.Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and 2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago. This continuing trend has made scientists concerned.There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous record high.With both air and water getting warmer,the ice is melting from both above and below. In some parts of the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning of the summer measured just 50 centimeters by season's end.The new measurements suggest that melting is far more severe than scientists have seen by just looking at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Researchand Engineering Laboratory in Hanover,N.H.Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.It can be learned from the last sentence that _________.A:the ice melt in the Arctic may never stopB:scientists are trying hard to stop the ice melt in the ArcticC:scientists are delighted to find out what is going on in the ArcticD:the warming trend in the Arctic can be reversed in the near future

点击查看答案
第6题

共用题干第一篇Arctic MeltEarth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice in the Arctic Ocean（北冰洋）fell to a record low.Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the summer. But for many years,the amount of ice left by the end of summer has been declining.Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and 2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago. This continuing trend has made scientists concerned.There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous record high.With both air and water getting warmer,the ice is melting from both above and below. In some parts of the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning of the summer measured just 50 centimeters by season's end.The new measurements suggest that melting is far more severe than scientists have seen by just looking at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Researchand Engineering Laboratory in Hanover,N.H.Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.The Beaufort Sea mentioned in Paragraph 7 is an example to show_________. A:how acetirate the new measurements areB:how thick the ice is in itC:how serious the problem of the ice melt in the Arctic isD:how dangerous it is to travel to it

点击查看答案
第7题

共用题干第一篇Arctic MeltEarth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice in the Arctic Ocean（北冰洋）fell to a record low.Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the summer. But for many years,the amount of ice left by the end of summer has been declining.Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and 2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago. This continuing trend has made scientists concerned.There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous record high.With both air and water getting warmer,the ice is melting from both above and below. In some parts of the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning of the summer measured just 50 centimeters by season's end.The new measurements suggest that melting is far more severe than scientists have seen by just looking at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Researchand Engineering Laboratory in Hanover,N.H.Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.What are the reasons for the ice melting according to the scientists?A:Strong winds and clear skits.B:Longer summers and shorter winters.C:Open water and thin ice.D:Heavy clouds and light winds.

点击查看答案

In cold, damp weather, the buildup of ice on airplane wings can pose significant aerodynamic problems. Which of the following effects would you expect?A.As ice builds up on the top of the wing, drag increases.B.As ice builds up on the top of the wing, lif

题目

更多“In cold, damp weather, the buildup of ice on airplane wings can pose significant aerodynamic problems. Which of the following effects would you expect?A.As ice builds up on the top of the wing, drag increases.B.As ice builds up on the top of the wing, lif”相关问题

第1题

第2题

第3题

第4题

第5题

第6题

第7题

相关内容