试题与答案

“神舟”六号飞船完成了预定空间科学和技术试验任务后,返回舱于2005年10月17

题型:问答题

题目:

“神舟”六号飞船完成了预定空间科学和技术试验任务后,返回舱于2005年10月17日4时11分开始从太空向地球表面按预定轨道返回。在离地l0km的高度返回舱打开阻力降落伞减速下降,返回舱在这一过程中所受空气阻力与速度的平方成正比,比例系数(空气阻力系数)为k。已知返回舱的总质量M =3000kg,所受空气浮力恒定不变,且认为竖直降落。从某时刻起开始计时,返回舱的运动vt图象如图中的AD曲线所示,图中AB是曲线在A点的切线,切线交于横轴于B点的坐标为( 10,0 ),CD是AD的渐近线,亦是平行于横轴的直线,交纵轴于C点,C点的坐标为( 0,6 )。请解决下列问题:(取g=10 m/ s2

(1)在初始时刻v0 = 160m/s时,它的加速度多大?

(2)推证空气阻力系数k的表达式并算出其数值;

(3)返回舱在距地高度h = 10m时, 飞船底部的4个反推力小火箭点火工作, 使其速度由6m/s迅速减至1m/s后落在地面上。若忽略燃料质量的减少对返回舱总质量的影响, 并忽略此阶段速度变化而引起空气阻力的变化, 试估算每支小火箭的平均推力(计算结果取两位有效数字)。

答案:

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参考答案:对

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Part 4


Questions 26-45


·Read the following article and choose the best word for each space.
·For questions 26-45, mark one letter A, B, C or D on the Answer Sheet.

iPhone Left in Hot Car for Three Hours


The normally peaceful suburban town of Winnetka is still reeling following the news Monday (26) a local resident, whose name is being (27) by police pending a full investigation, left an iPhone unattended for more than three hours in a car (28) in the hot sun.
"Responding to calls from (29) . passersby, who observed the iPhone sitting in a vehicle in the parking (30) of the Westfield Shopping Center, police arrived on the (31) at approximately 4 p.m. and immediately intervened to save the device," said Winnetka police chief Douglas Blaine. "Security cameras have shown that the iPhone had been in the car— with the doors (32) and the windows rolled (33) —since 1 p.m. Due to the tragic and highly emotional (34) of this case, we cannot say any (35) at this time."

A. admissionB. examinationC. operation D. function

According to official police records, two officers forcibly (36) into the car at 4:07 p.m. and found the iPhone (37) face down on the dashboard. The iPhone at first showed no (38) of life, but after a tense few seconds, officers were able to wake it and get it to (39) to a series of simple touch commands. Police said that if the iPhone were left in the extreme (40) for any longer, it could have died.
The iPhone was rushed by ambulance to a nearby Apple facility for careful (41) .Miraculously, no damage to its memory, screen, or wireless capabilities was reported.
Upper-middle-class suburbanites from all over the North Shore area have reacted to the near-tragedy with an unprecedented outpouring of (42) . Hundreds of cards and letters have come streaming in, and local talk radio shows have been flooded (43) calls demanding that the iPhone’s (44) be prosecuted. Many have come forward offering to take the iPhone into their custody, and still (45) have donated free downloads, ringtones, and MP3s to the victimized object.

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