问题 问答题

小明同学在初中物理探究实验时发现:

(1)当要研究的物理量不易直接测量时,都要想办法把它们的大小间接表示出来.这种研究方法的名称叫转换法.如:图甲的实验是通过______,间接的比较物体动能的大小;图乙的实验是通过______,间接比较两个电阻丝产生的热量的多少.

(2)当要研究的物理量与多个因素有关时,都要采用控制变量法.

如:图甲的实验中,使用同一个球就是为了探究动能大小与______的关系;图乙中将两个电阻串联起来,就是为了探究电流产生的热量与______的关系.

(3)有些实验装置经过适当的改进还可以进行其它的探究实验.如:图甲装置中增加一个弹簧测力计等器材,我们还可以探究斜面的机械效率是否与物体的重力有关;图乙中如果再增加一个______,我们就可以探究电流产生的热量与电流大小的关系了.

答案

(1)动能的大小不能直接观察,但木块被推出的距离可以直接观察,所以用木块被推出距离的远近判断小球动能的多少;电流通过电阻丝产生的热量多少不能直接判断,但液体温度的变化可以通过温度计测量,所以从温度计示数变化大小能够判断电流产生热量的多少.

(2)动能多少与物体的质量和运动速度有关,使用同一个球质量一定,探究的是速度对动能的影响;串联电路各处电流都相等,两电阻串联,目的是电流相等,研究热量与电阻大小的关系.

(3)研究电流产生热量与电流大小关系时,要保持电阻一定,改变电路中的电流,所以要在电路中串联一个滑动变阻器.

故答案为:(1)木块被推动的距离;温度计示数的变化量;(2)质量;电阻;(3)滑动变阻器.

单项选择题
单项选择题

Questions 21~25


While other members of my team explored the wreck of a small Greek merchant ship that sank off the Turkish coast more than 2,400 years ago, I hovered above them in a submarine. One diver, an archaeologist, placed an amphora, or two-handled jar, inside a lifting basket. Another vacuumed sediment from the site by fanning sand into the mouth of a nearly vertical pipe. Two more were taking measurements, carefully, but of necessity quickly, for at this depth each diver had only 20 minutes to complete the morning’s assigned task. Any longer, and they would require lengthy medical treatment, to avoid the divers’ ailment known as the bends.
In four decades of diving on shipwrecks, I’ d been too engrossed in carrying out similar tasks to think of the families whose loved ones may have disappeared long ago. I had always concentrated on the technical features of my trade. I had stopped diving regularly 15 years before this exploration, turning over the bulk of the underwater work to a younger generation, but I continue to make inspection dives on most wrecks we excavate.
This was not just any wreck. Although I’ve been involved in uncovering the remains of much older ships, and of more than a hundred ancient shipwrecks along the Turkish coast. I had never even seen a wreck from the fifth century BC. Preliminary photographs of the cargo dated it to the third quarter of the century, during the Golden Age of classical Greece. Athens, then as now the major city in Greece, controlled an empire stretching from one side of the Aegean Sea to the other. None of this would have been possible without naval might and maritime commerce.
During our three-year exploration of the wreck we excavated examples of nearly every type of jar that the classical Greeks made for wine or water. Many types might have been used as tableware by the ship’s crew, but they were far in excess of what would have been required. We concluded therefore that they must have been cargo. We also discovered in the seabed two marble discs, which we guessed were the ship’s eyes. It has long been known from vase paintings that classical Greek ships—like those from other cultures—had eyes to give them life or help them see their way through the waves. Although warships were known to have had naturalistic marble eyes attached to them, most scholars assumed that the eyes on more modest merchant ships were depicted as simple circles painted onto the sides of the vessel.
Did the sailors who depended on these eyes for safety survive the ship’s last voyage They could have lived through the actual sinking. The ship was less than a hundred yards from land when it sank, so they might have swum towards the shore. And we know from Greek literature that some ships had lifeboats. But proximity to land and having lifeboats are no guarantee of safety. Even if some had swum to shore, it’s hard to imagine that many managed to crawl up on the exposed and sharp rocks while being smashed by waves like those that almost certainly sank their ship.

The writer uses the words’not just any wreck’ in paragraph 3 to imply that ______.

A. he had been searching for the ship for a considerable time
B. this was not the only ship found off the coast of Turkey
C. finding this particular ship was of exceptional significance
D. the ship was in better condition than most wrecks