问题 计算题

(14分)在某市某一旅游景区,建有一山坡滑草运动项目. 该山坡可看成倾角θ=30°的斜面,一名游客连同滑草装置总质量m=80kg,他从静止开始匀加速下滑,在时间t=5s内沿斜面滑下的位移x="50m." (不计空气阻力,取g=10m/s2,结果保留2位有效数字)问:

(1)游客连同滑草装置在下滑过程中受到的摩擦力F为多大?

(2)滑草装置与草皮之间的动摩擦因数μ为多大?

答案

(1)80N (2)0.12

题目分析:(1)由位移公式  

沿斜面方向,由牛顿第二定律得:

 

联立并代入数值后,得

  

(2)在垂直斜面方向上

   

   

联立并代入数值后,得

点评:中等难度。本题已知物体的运动情况,根据运动学公式求出物体的加速度,再根据牛顿第二定律确定物体所受的力.在处理动力学的两类基本问题时,加速度是联系运动和力的纽带、桥梁。

填空题
阅读理解

The English are famous for their manners. The phrase, “Manners maketh the man” was coined by Englishman William of Wykeham back in 1324, but they’re just as important today. Books are written on the subject, advice columns in magazines tell people how to behave, and “finishing schools” still exist to ensure that young girls become young “ladies”.

The best example of English manners is in their mastery of the art of forming a queue. It is a popular joke in England (the land of sporting failures) to say, “if only queuing was an Olympic sport, we’d win hands down” No one knows exactly how and when it started, but queuing plays an important role in the English social make-up. School children are taught to queue for roll-call, assembly and lunch, and English people across the land form orderly queues at shops, banks, cinemas and bus-stops every day. The English obviously aren’t the only people who queue, but they seem to do it better than anyone else. As one visitor said, “I have travelled across Europe, the Middle and Far East and nowhere have I seen the single-file queues which are formed in England.”

The English are also famously polite when it comes to language. Whereas many other notions are more direct in their communication, the English prefer a more indirect form of asking for things. For example, an American who wants to talk to a colleague might say, “Got a minute?”; however an English person will often use a more indirect means might of requesting the chat, “Sorry to bother you, but would you possibly have a minute or so to have a quick chat if you don’t mind, please?”

The English also love to apologize for things. When squeezing past someone, people say “sorry”. And they will apologize if you bump into them, “whoops! Sorry! My fault.” In fact, no one seems to say “sorry” as much as the English: “sorry I’m late. /Sorry I forgot to call you last night./I’m sorry you didn’t get the e-mail.” And so on. They also like to use “please” and “thank you” a lot. In a shop, they will say, “I’d like a packet of crisp, please. Thanks.” British students thank their lectures, and bosses often thank their employees for doing their jobs.

小题1: Why does “finishing schools” still exist to help young girls become “ladies”?

A.Because the English mind their manners very much.

B.Because the English parents want to marry their daughters to the royal family.

C.Because the English girls are so rude that they need to be taught to be polite.

D.Because the English government ensures their existence.小题2:The underlined sentence in paragraph2 implies ________________.

A.The English love the Olympics very much.

B.The English spend nothing winning an Olympic medal.

C.The English are best at queuing.

D.The English prefer to queue with their hands down.小题3: According to the passage, if Americans say “Waiter! Could I have another fork, please?” how will the English express such a meaning?

A.Excuse me! Give me another fork, please!

B.Excuse me! I have to be a bother, but would you mind awfully changing this fork, please?

C.Hi! Would you mind giving me another fork?

D.Waiter! Come here and change the fork!小题4:According to the passage, why do the employers often thank their employees for doing their jobs?

A.The employees can bring them a lot of benefits.

B.The employees finish their jobs perfectly.

C.The English employers’ good manners lead them to do so.

D.The employers do it as a result of the company’s regulation.