问题 实验题

图1为验证牛顿第二定律的实验装置示意图.图中打点计时器的电源为50Hz的交流电源,打点的时间间隔用Δt表示.在小车质量M未知的情况下,某同学设计了一种方法用来研究“在外力一定的条件下,物体的加速度与其质量间的关系”.

(1)完成下列实验步骤中的填空:

①平衡小车所受的阻力:撤去砂和砂桶,调整木板右端的高度,用手轻拨小车,直到打点计时器打出一系列     的点.

②按住小车,在左端挂上适当质量的砂和砂桶,在小车中放入砝码.

③打开打点计时器电源,释放小车,获得带有点迹的纸带,在纸带上标出小车中砝码的质量m.

④按住小车,改变小车中砝码的质量,重复步骤③.

⑤在每条纸带上清晰的部分,每5个间隔标注一个计数点.测量相邻计数点的间距s1,s2,….求出与不同m相对应的加速度a.

⑥以砝码的质量m为横坐标,为纵坐标,在坐标纸上做出-m关系图线.若加速度与小车和砝码的总质量成反比,则与m应成     关系(填“线性”或“非线性”).

(2)完成下列填空:

①本实验中,为了保证在改变小车中砝码的质量时,小车所受的拉力近似不变,悬挂砂和砂桶的总质量应满足的条件是     .

②如图2所示是该同学在某次实验中利用打点计时器打出的一条纸带,A、B、C、D是该同学在纸带上选取的连续四个计数点.该同学用刻度尺测出AC间的距离为S,测出BD间的距离为S.a可用S、S和Δt(打点的时间间隔)表示为a=     .

  

③图3为所得实验图线的示意图.设图中直线的斜率为k,在纵轴上的截距为b,若牛顿定律成立,则小车受到的拉力为     ,小车的质量为     .

答案

(1) ①等间距 ⑥线性(2)①远小于小车和砝码的总质量;②

题目分析:(1)①平衡小车所受的阻力:撤去砂和砂桶,调整木板右端的高度,用手轻拨小车,直到打点计时器打出一系列等间距的点;⑥以砝码的质量m为横坐标,为纵坐标,在坐标纸上做出-m关系图线.若加速度与小车和砝码的总质量成反比,则与m应成  线性关系;(2)①本实验中,为了保证在改变小车中砝码的质量时,小车所受的拉力近似不变,悬挂砂和砂桶的总质量应满足的条件是远小于小车和砝码的总质量;②根据,则,所以③根据牛顿定律,变形可得:,所以,解得:

阅读理解

阅读理解。

     Sun Miao is eight years old. He often plays badminton (羽毛球) after his father comes back from

the factory, He often plays table tennis after his mother comes back from her hospital. He can play them

very well.

    One afternoon, when he comes out of  the classroom, he sees his father waiting for (等) him at the

school gate. He is very glad and runs to his father. "Dad, please don't wait for me after school. I can go

home by myself , " says Sun Miao.

    "Let's go," says the father. "I'll do the cooking and you can do your homework at home. Your mother

 is still at work. "

     When they are on their way home,Sun Miao sees some boys skating in the park.

      "Can I go and skate, Dad?" asks Sun Miao.

      "I'm sorry, my boy. You can't go there. You must go home and do your homework , " answers

the father. "And I think I can give you some ice cream.

1. There are ________ people in Sun Miao's family.     

A. two     

B. three     

C. tour      

D. five   

2.  Sun Miao's father is a ________.      

A. doctor     

B. student     

C. teacher

D. factory worker

3. Sun  Miao plays ________ after his father comes back from work.     

A. table tennis     

B. volleyball     

C. badminton     

D. football

4.Who often takes Sun Miao home after school?      

A. His father.     

B. His mother.     

C. His classmate. 

D. His good friend.

5. Sun Miao's father asks him to go home to ________.

A. do the cooking

B. do his homework

C. help him cook

D. buy ice cream

选择题