问题 计算题

如图,质量M=8.0kg的小车停放在光滑水平面上。在小车右端施加一个F=8.0N的水平恒力。当小车向右运动的速度达到3.0m/s时,在其右端轻轻放上一个质量m=2.0kg的小物块(初速为零),物块与小车间的动摩擦因数μ=0.20,假定小车足够长。求:

(1)经多长时间物块停止在小车上相对滑动?

(2)小物块从放在车上开始,经过t=3.0 s,通过的位移是多少?(取g=10m/s2

答案

解:(1)对物块:μmg=ma1,∴a1=μg=2m/s2

对小车:F-μmg=Ma2,∴a2=0.5m/s2

物块在小车上停止相对滑动时,速度相同

则有:a1t10+a2t1

∴t1=

(2)t1物块位移x1=

t1时刻物块速度υ1=a1t1=4m/s

t1后M、m有相同的加速度,对M、m整体有:F=(M+m)a3,∴a3=0.8m/s2

∴x21(t-t1)+=4.4m

∴3S内物块位移x=x1+x2=8.4m

阅读理解

请阅读下列交友信息,并按照要求匹配信息。请在答卷上把对应题号的相应选项的字母写出来。(请将该部分答案涂在电脑答题卡上,AB同时涂黑代表E;CD同时涂黑代表F。)

A.Piotrek Kowalski, 18, from Italy. Looking for a pen friend who is interested in discussing the current (当前的) political situation in the world. Like jazz and playing tennis in my free time.

B. Olga, 32 years old, historian, from Warsaw, Poland. Looking for a pen friend to exchange views on the political problems in East European countries after the Second World War.

C. Jack, 27, from London. My favorite pastime (消遣) is learning foreign languages. I go to evening language classes and use my computer to improve my language learning by visiting Internet sites.

D. Elle, 35 years old, from Paris. I like learning languages, but do not like using modern technology. Need a pen friend who also enjoys learning languages in a traditional way.

E. Petro, 42, businessman, from Argentina. Trying to get a pen friend with the same profession(职业) and lives in North America. Married, with three children and like surfing the Internet.

F. Kim Lee, 18, high school student in Seoul, South Korea. I love traveling and hope to visit Great Britain in the future. I would like a friend about the same age to get some information about the differences between life in Europe and that in Asia.

以下是交友者的信息。请匹配交友者与他们所对应的信息。

小题1:Mary, 21, a university student on history, comes from Scotland and would like to find a pen friend who comes from East Europe. She is interested in the things of the past in those countries.

小题2:Helga, 33, comes from Germany and speaks French, English and Russian. She prefers a pen friend who is also fond of exchanging ideas about language learning by writing letters and she firmly believes that language learning can only happen in a classroom.

小题3:Alessandro, 25, comes from Rome. He is interested in finding a pen friend who speaks English and can exchange ideas on using the computer for learning purpose.

小题4:Bob, 17, a middle school student in Liverpool, is interested in making a pen friend. He once visited China with his parents when he was a child and then fell in love with Asian culture. He would like a friend of the same or nearly the same age.

小题5:Jim, 35, has a company in Boston. His hobby is surfing the Internet in his spare time and looking for any useful information for him, whether at home or abroad.

单项选择题 A1/A2型题