问题 问答题

高压起重气垫是一种适合于地震救灾的起重工具。它由如图甲所示的高压气瓶、气管、阀门与气垫连接而成。起重时,气垫放入重物与地面的间隙之间,由高压气瓶向气垫内充气,气垫在短时间内可把重物举起一定高度。

(1)高压气瓶向气垫内充气时,气瓶内的气体温度_______,内能_______。如果高压起重气垫在5s内可将105N的物体举高0.1m,则其功率为________W。

(2)图乙中,质地均匀的长方体石板长为2m、重为6×104N。当气垫内最高气压比外界高106Pa时,石板恰好被顶起,此时气垫和石板的接触面是连长为20cm的正方形。

①请在图乙中画出气垫恰好顶起石板时的阻力臂l2

②气垫恰好顶起石板时,气垫的中心至少离石板右端的支点O多远?

答案

解:

(1)降低;减少;2×103

(2)

①气垫刚好顶起石板时的阻力臂l2如图所示:

②F1=pS=106Pa×0.2m×0.2m=4×104N

根据F1l1=F2l2得:l1===1.5m。

单项选择题
单项选择题


In the following passage, there are 20 blanks representing words that are missing from the context. Below the passage, each blank has 4 choices marked by letter A, B, C and D respectively. There is only ONE right answer. Blacken the corresponding letter as required on your Machine-scoring ANSWER SHEET.

How many of us would temp for three years while we waited for the perfect job Not many of us, perhaps. But Wentworth Miller, the "Prison Break" star, said he chose to wait even longer time (91) he found the right job.
"Actually I think it might have been three or four years until I was lucky enough to get guest (92) on TV shows," said Miller, 34, who rose to international stardom (93) to "Prison Break" in 2006. That kind of patience and p will was portrayed in "Prison Break". Miller (94) engineering wizard Michael Scofield, who tries everything to break out of a Chicago (95) with his brother. Miller said he was fond of his character, (97) he said "exists in shades of grey".
Miller comes from a (97) of teachers. He said he didn’t seem fated for a career in the arts, (98) his passion for acting. After (99) from Princeton with an English degree, he moved (100) his parents’ request to Los Angeles to look for a stable life. He started (101) in a little company that made television movies. This (102) simply faxing, filing, walking the boss’ dog and going to the store for the boss’ lunch. Every weekend during the summer, Miller (103) go to the office (104) he didn’t have air-conditioning. "I would hang (105) in the conference room and set up camp and rob the company kitchen," recalled Miller.
(106) , Miller realized he still had questions about his choice. He decided to quit. But the boss said he was making a mistake and offered him a well-paid assistant position. "I eventually (107) that if I did the corporate job, it would be great if I was successful, but I would always wonder about the (108) . If I did the acting and was successful, I would never wonder (109) that job," he explained. He quit and temped (110) many people in the entertainment industry.

A.would

B.should

C.might

D.ought to