问题 实验题

如图甲所示为测量电动机匀速转动角速度的实验装置,半径不大的圆形卡纸固定在电动机转轴上,在电动机的带动下匀速转动.在圆形卡纸的旁边垂直安装了一个改装了的电火花计时器.

(1)请将下列实验步骤按先后排序:________

A.使电火花计时器与圆形卡纸保持良好接触

B.接通电火花计时器的电源,使它工作起来

C.启动电动机,使圆形卡纸转动起来

D.关闭电动机,拆除电火花计时器;研究卡纸上留下的一段痕迹(如图乙所示),写出角速度ω的表达式,代入数据,得出ω的测量值。

(2)要得到ω的测量值,还缺少一种必要的测量工具,它是________.

A.秒表    B.毫米刻度尺     C.圆规    D.量角器

(3)写出角速度ω的表达式,并指出表达式中各个物理量的意义。

答案

(1)ACBD  (2)D  (3)  θ为n个点对应的圆心角,T为时间间隔

题目分析:(1)该实验步骤中必须让电动机带动卡纸匀速转动,然后接通电火花计时器,因为要测量电动机转动的角速度,不能让电动机不动之前,就接通电火花计时器,这一点很特别。因此次序是ACBD。

(2)要测量角速度,根据角速度的定义,除了用电火花计时器测量时间之外,还需要一种仪器测量角度,因此选项D正确。

(3)根据公式可得:,其中θ为n个点对应的圆心角,t为时间间隔。

翻译题
阅读理解

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小题1:Anyone who takes an interest in the crime rate will, according to the text, be aware that ___________.

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D.homes are more likely to be broken into nowadays小题2:It seems that people who live in cities are ____________.

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B.Fingers

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