问题 填空题

如图所示,质量为m、边长为L的等边三角形abc导线框悬挂于水平轻杆一端,离杆左端1/3处有固定转轴O,杆另一端通过细线连接地面.导线框处于磁感应强度为B的匀强磁场中,且与磁场垂直.当线圈中逆时针电流为I时,bc边所受安培力的大小及方向是______;接地细线对杆的拉力为______.

答案

bc边所示安培力大小F=BIL,

由左手定则可知,安培力的方向竖直向上;

由于导线框闭合,所受安培力为零,

因此导线框对杠杆的拉力等于其重力mg,

由力矩平衡条件可得:mg×

1
3
L=F×
2
3
L,

则细线对杆的拉力F=

mg
2

故答案为:大小:BIL,方向:竖直向上;

mg
2

填空题
完形填空

阅读下面短文并回答问题,然后将答案写到答题卡相应的位置上(请注意问题后的词数要求)。

[l] We expect companies selling products to make them as available as possible. But now some of them are bringing back rationing(定量供应). As you might expect, it's all part of a plan to make us spend more, not less.

[2]Butter, bacon, sugar, tea and meat were rationed in Britain during World War II, because goods at that time were scarce, and hard to get for all. But nowadays industrial mass production           . Factories all over the world are pumping out bright and beautiful objects.

[3]When everyone has to wait and save up for new things, owning them feels exciting and special. But when lovely things are available every day, they stop being a treat. The other characteristic of consumer society is that we aim for social distinction through what we own. But if everyone has lots of things, how can we impress anyone with our purchases? All of this takes the fun out of shopping and means there's a limit to how much consumerism can grow.

[4] This is deeply worrying to companies, and some of them have started to fight it, by creating artificial scarcity(短缺). For example, Swedish rapper Adam Tensta has limited access to his latest track. Only one person at a time can access it, and fans must take their place in a digital queue.

[5] This hend means we can again own something rare. But the risk for these companies is that in a world of so many things, if they make their products too hard to get, we'll just buy from someone else instead.

小题1:What is the text mainly about? (no more than 3 words)

                                                                               

小题2:Fill in the blank in Paragraph 2 with proper words. (no more than 5 words)

                                                                               

小题3:In which paragraph can the following sentences be put as an example?

In Singapore, a small cafe called Liberty Coffee only opens on random days. It sometimes stays closed for over a week at a time.

                                                                               

小题4:What are the two characteristics of consumer society? (no more than 15 words)

                                                                           

                                                                           

小题5:What is the risk for the companies creating artificial scarcity ? (no more than l0 words)