问题 问答题

中国“辽宁号”航空母舰是中国人民解放军海军的第一艘航空母舰.2012年9月25日,该舰正式加入中国海军序列.11月25日,歼-15舰载机在航母上成功起降,为中国航母战斗力的形成迈出了极为关键的一步.歼-15舰载机是我国自行设计研制的首型舰载多用途战斗机,具有完全的自主知识产权.航空母舰上的起飞跑道可以简化为如图所示的情境,假设航空母舰上的起飞跑道由长度为l1=1.6×102m的水平跑道和长度为l2=20m的倾斜跑道两部分组成.水平跑道与倾斜跑道末端的高度差h=4.0m.舰载机质量为m=2.0×104kg,其发动机的推力大小恒为F=1.2×105N,方向与速度方向相同,在运动过程中舰载机受到的平均阻力大小为舰载机重力的0.1倍.假设航母处于静止状态,舰载机质量视为不变并可看成质点,取g=10m/s2

(1)求舰载机到达倾斜跑道末端时的速度大小;

(2)为了使舰载机在倾斜跑道的末端达到起飞速度100m/s,外界还需要在整个水平轨道对舰载机施加助推力,求助推力F的大小.

答案

(1)设舰载机到达倾斜跑道末端时的速度大小为v,全过程运用动能定理得,

(F-Ff)(l1+l2)-mgh=

1
2
mv2-0

代入数据解得v=41.5m/s.

(2)由题意知,只有水平轨道对舰载机施加助推力F,全过程运用动能定理得,Fl1+(F-Ff)(l1+l2)-mgh=

1
2
mv2-0

将v′=100m/s代入解得F=5.2×105N

答:(1)舰载机到达倾斜跑道末端时的速度大小为41.5m/s.

(2)助推力F的大小F=5.2×105N

填空题
单项选择题

The questions in this group are based on the content of a passage. After reading the passage, choose the best answer to each question. Answer all questions following the passage on the basis of what is stated or implied in the passage.

One of the biggest questions facing the art world today is the dilemma over the repatriation of cultural treasures. Although the subject has not been widely noted by the general public, in recent decades museums and art dealers have repeatedly faced off against the representatives of nations and ethnic groups whose cultural legacies have been robbed by the rapacious collecting of these so-called art experts. Advocates of repatriation have argued that cultural treasures should be returned to their nations of origin, both because of basic fairness and because the artwork and cultural artifacts in question are best understood within their local context.

Several prominent museums, most notably the British Museum in London and the Louvre in Paris, have defended themselves on the grounds that they can better protect and preserve these cultural treasures than can the developing nations and impoverished ethnic groups that frequently seek their return. They further argue that more people can see the treasures if they are proudly displayed in a major museum, as opposed to some poorly funded national museum in a backwater country; evidently, the quantity of viewers is more important than the relevance of the art and artifacts to the viewer.

The arguments of the museum curators fall apart in an instance such as the Elgin Marbles. These majestic marble sculptures, which once graced the Parthenon on the Acropolis in Athens, were stolen by Lord Elgin in the nineteenth century and given to the British Museum, which holds them to this day. The people of Athens have built a beautiful, modern museum on the Acropolis to display the Elgin Marbles and other treasures from the Greek cultural heritage, so there can be no valid argument that the Greeks are unable to house the sculptures properly. Furthermore, more people visit the Acropolis every day than visit the British Museum.

Of the following, the most appropriate title for the passage above would be:()

A. The Elgin Marbles: Timeless Symbols of the Glory That Was Greece

B. The Role of Great Museums in the Preservation of Cultural Artifacts

C. Repatriation of Cultural Treasures: The British Museum’s Dirty Little Secret

D. The Value of Cultural Treasures in Defining National Identity

E. A Curious Curator: Lord Elgin and the Rise of the British Museum