问题 填空题

请你运用所学物理知识指出以下“特异功能”的真相.表演者从沸腾的油锅中取物,手却未被烫伤.真相:锅中除了植物油,还渗有下表中的物质为______,因为它具有______、______的属性.

物质酒精植物油
密度(g/cm3约1.30.80.9
沸点(℃)约3575约280

答案

表演时,因为醋的密度大,所以会沉在油的下面.上面的植物油吸收的热量主要是来自下面的醋,醋达到沸点后温度不再升高,上面的油达到醋的沸点后,不再发生热传递,温度也不再升高.所以当人从锅里取物时,其实温度并不是特别高(35℃左右),手不至于烫伤.

故答案为:醋;密度大;沸点低.

单项选择题

Questions 53 to 57 are based on the following passage: ( 10 分 )  How did a peddler of cheap shirts and fishing rods become the mightiest corporation in America The short version of Wal-Mart’s rise to glory goes something like this:in 1979 it racked-up a billion dollars in sales; by 1993 it did that much business in a week; by 2001 it could do it in a day.  It’s a shocking tale--one that propelled Wal-Mart from rural Arkansas, where it was founded in 1962, to the top of the Fortune 500. Sam Walton, Wal-Mart’s founder, pushed sales growth continuously while squeezing costs with sophisticated information technology. He exhorted employees to sell better with the "ten-foot rule" ( greet customers if they are that close ). He was, in other words, an early evangelist for the first commandment of today’s economy: service rules. Wal-Mart, in fact, is the first service company to rise to the top of the Fortune 500. When Fortune first published its list of the largest companies in America in 1995, Wal-Mart didn’t even exist. That year General Motors was America’s biggest company, and in every year that followed,either GM or another mighty industrial, Exxon, was No.1.  Wal-Mart’s achievement caps a bigger economic shift I from producing goods to providing services. Manufacturing’s share ofU. S. employment peaked in 1953, at 35%. It has been declining steadily since. In the decade that will end in 2010, the Bureau of Labor Statistics figures that goods-producing industries will create 1.3 million new jobs, compared to 20 million for service industries. To look at it another way, today there are about four times as many people working in service jobs as in other kinds of jobs. And even within manufacturing, services are an increasingly large share of operations.  As America got richer, consumption got more complicated. With more income to throw around, people started spending more on services -- movies and travel, mortgages to buy houses, insurance to protect those houses, the occasional weekends at a luxury hotel. Fortune calls this a shift in the demand pattern. Over the next few years, only three of the ten fastest-growing occupations ( software engineers, nurses, and computer support ) pay middle-class salaries. The rest could be called Wal-Mart kinds of jobs -- cashiers, retail assistants, food service, and so on. In short, the service economy is delivering more good jobs than ever before.

According to Fortune, Wal-Mart’s rise is mainly the result of__

A.the decline of goods-producing industries

B.the rise of the middle class

C.a shift in the demand pattern

D.Sam Walton’s hard work

单项选择题