题目

某同学在“探究小车速度随时间变化的规律”的实验中，用打点计时器记录了被小车拖动的纸带的运动情况，在纸带上确定的A、B、C、D、E、F、G共7个计数点，其相邻点间的距离如图所示，每两个相邻计数点之间还有四个点未画出。试根据纸带上各个计数点间的距离。 (1)在做用打点计时器测速度的实验时，要用到打点计时器，打点计时器是一种        仪器，其电源频率为        Hz ，常用的电磁打点计时器和电火花计时器使用的电源 是    �根据句意及括号中所给汉语、单词完成句子，注意正确形式。每空限填一词。1.I often play __________ (排球) with my friends after school.2.I like the house. ___________ (然而), I don’t have enough money.3.I am bad at playing baseball and I usually ____________(未击中) the ball.4.Jack’s biggest hobby is reading _________ (小说).5.In the ____________ (末尾), Anna lost the good chance.6.The Yangtze River is __________ (wide) than the River Thames.7.They ____________ (raise) much money for the poor children yesterday.8.Do we have a good _____________ (choice)？9.Don’t be afraid of making _________ (mistake) when you speak English.10.Tom, please drive ___________ (careful) on rainy days.