某兴趣小组的同学们在做“用打点计时器测速度”的实验中，让重锤自由下落，打出的一条纸带如图所示，图中直尺的单位为cm，点O为纸带上记录到的第一点，点A、B、C、D…依次表示点O以后连续的各点．已知打点计时器每隔T=0.02s打一个点．
（1）打点计时器打下点G时重锤的速度可用表达式vG=______进行计算，式中各量的意义是______
（2）用上式计算出打下点G时重锤的速度为vG=______m/s．
（1）纸带实验中，可以用平均速度代替中点时刻的瞬时速度，
则：vG=
，其中FH表示F、H两点间的距离，T表示周期；FH 2T
（2）vG=
=FH 2T
m/s=1.30m/s0.052 0.04
故答案为：vG=
；FH表示F、H两点间的距离，T表示周期；1.3FH 2T
每个案例有多个提问，每个提问有5～8个备选答案，其中正确答案有1个或者多个。
| 男性患者，24岁，1周前“感冒”，2d前出现双下肢无力，伴尿潴留，并逐渐加重。查体：双下肢远端肌力 0级，肌张力减低，剑突以下全部感觉及浅反射消失，腱反射减弱，Babinski征阴性，膀胱充盈平脐，脊柱无压痛。 |
考虑诊断最可能为
A．脊髓灰质炎
B．急性横贯性脊髓炎
C．多发性硬化
D．脊柱转移性肿瘤
E．急性硬膜外脓肿
| Ever since it was claimed that a medicine made from the Chinese three-striped box turtle could cure cancer, demand for the product has increased, making the turtle the most expensive to be found in China’s food markets. Huge sums of money have been made selling the medicine. The turtle -- along with a few other Cuora species -- was once imported into China by the pet trade. Exporters obtained the specimens in the food markets rather than going out to collect them in the wild. Treatment of the turtles prior to reaching the markets resulted in many of them being diseased. Packed tightly into crates, often for journeys of several weeks without food, it is little wonder that many specimens exported to western countries fared poorly when purchased as pets. Throughout the Far East turtles and tortoises have featured in various cultures and certain religions. They have also been used for hundreds of years for food and medicine. Traditional Chinese medicine is probably the greatest threat to the three-striped box and to the thousands of other turtles that are imported yearly into China. Turtles are well known for their longevity, which it is thought will be passed on to those eating them. Turtle blood, bones and shells -- particularly the plastron (ventral part of the shell) -- are thought to have medicinal properties and be able to cure a number of ailments. Turtle eggs are also used for food and medicine. The medicinal value of the turtles is open to question, and it is possible that herbs could produce the same effects. Any beneficial substances from the turtles could also be synthesized chemically, so as to prevent the killing of turtles. The southern part of China has become more prosperous in recent years, and the demand for turtles has increased dramatically. Turtle dishes are served in restaurants and regarded as an expensive delicacy, even a status symbol. As turtle supplies in China dwindled, traders started importing the animals from Vietnam. As a result, many Vietnamese turtles have now disappeared from their haunts in the wild. To satisfy growing demand, importers have now turned to sources farther afield, including Cambodia, Laos, Nepal, India, Bhutan and Indonesia. Since biologists started studying turtles in Chinese food markets, several previously unknown and extremely rare species have been found; some are on Appendix I of CITES. At the present rate of collection such specimens, and even species not yet discovered, could soon be extinct. The three-striped box turtle is simply one among dozens of other species flooding into China, but its high value makes it a special target for collectors. |
The noun phrase "the medicine" underlined in Paragraph 1 refers to the ______.
A．turtle
B．medicine made from turtle
C．cancer cure
D．pet trade