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电磁打点计时器和电火花计时器都是一种仪器，当电源的频率为50Hz时，这两种仪器打点的时间间隔都为______s．某次实验时，当物体做匀加速直线运动时，某同学得到了几条较为理想的纸带，他已在每条纸带上按每5个点取一个计数点，即所取两计数点之间的时间间隔为0．ls，依打点的先后次序编为0、l、2、3、4、5．由于不小心，几条纸带都被撕断了，请根据如图所示的A、B、C、D四段纸带回答：

（1）在B、C、D三段纸带中，有一段是从纸带A上撕下的，你认为从纸带A上撕下的那段应该是______

（2）打A纸带时，物体的加速度大小是______m/s2．

（3）打A纸带上的点l时，物体的瞬时速度是______m/s．

答案

电源频率是50Hz，则打点的时间间隔T=

1
f
=
1
50Hz
=0.02s；

（1）由图示可知，纸带A上相邻计数点间的间隔是6mm，图C中4、5点间的间隔与A上1、2点间的间隔之差是18mm，正好是6mm的3倍，则纸带C是从A上撕下的．

（2）纸带A的加速度a=

x12-x01
t2
=
0.036-0.030
0．12
=0.6m/s2；

（3）纸带A上，打点1时的瞬时速度v=

x02
2t
=
0.030+0.036
2×0.1
=0.33m/s；

故答案为：0.02；（1）C；（2）0.6；（3）0.33．

多项选择题

生产任务卡应该反映（）等内容。

A.菜品准备总数

B.生产方式和份额

C.厨房库存与待购买或领用量

D.预计结存量
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填空题

Many animals engage in play，but homo sapiens is the only animal (1) have invented sports.Since sports are an invention，a part of culture (2) than an aspect of nature，all definitions of sports are somewhat arbitrary. (3) sports are a human universal found in every known culture or a (4) unique to modern society depends upon one’s definition of sports.Men and (5) have always run，jumped，climbed，lifted，thrown， and wrestled，but they have (6) always performed these physical activities competitively. Although all literate societies seem to (7) contests of one sort or another in which men， and sometimes women， (8) in displays and tests of physical skill and prowess，sports may be (9) defined as physical contests performed for their own sake and not for (10) ulterior end.According to this strict definition，neither Neolithic hunters nor contestants (11) religious ceremonies such as the ancient Olympic Games were engaged in sports. (12) on the stipulation that sports must be performed for their own sake (13) the paradoxical elimination of many activities which are usually thought of as (14) ，such as exercises done for the sake of cardiovascular fitness，races run (15) satisfy a physical education requirement，ball games played to earn a paycheck. (16) definition also means abandonment of the traditional usage in which"sport，"derived (17) Middle English disporter，refers to any light hearted recreational activity.In the. (18) of some 18th- century aristocrats，a game of backgammon and the seduction of (19) milkmaid were both considered good sport，but this usage of the term (20) become archaic.
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