问题 阅读理解

阅读短文并回答问题。

      Look! There are some students sitting in the classroom. They are reading books. The boy on the left

side is Jim. The girl behind him is Sue. Alice is the shortest in the class. She sits in the first row. Who are

they at the back of the classroom? They are Li Lei and Wang Gang. They are taller than others in the class.

Is the girl in the middle Lucy? Yes, she is, and her sister is on her right. They are twins. They are new

students. We like them very much.

1.Are there any students in the classroom?

     _____________________________________________________________________

2.What are they doing?

     _____________________________________________________________________

3.Who is the girl behind Jim?

     _____________________________________________________________________

4.Where are Li Lei and Wang Gang sitting?

     _____________________________________________________________________

5.Why do they sit at the back of the classroom?

     _____________________________________________________________________

答案

1. Yes, there are.

2. They are reading books.

3. The girl behind Jim is Sue.

4. They are at the back of the classroom.

5.  Because they are taller than others in the class.

实验题

快速骑自行车,我们会感到空气阻力,而且骑车速度越快,感觉空气阻力越大.由此小华同学猜想:物体所受空气阻力大小与物体运动的速度大小有关.

在一个无风的周末,小华和爸爸开汽车来到郊外一段人车稀少的平直公路上.小华打开汽车天窗,将如图所示装置固定在汽车车顶.爸爸依次以5m/s、10m/s、15m/s、20m/s的不同速度在平直公路上各匀速行驶一段距离,小华依次将汽车不同行驶速度时的弹簧测力计的示数记录在下表中.根据二力平衡.弹簧测力计的示数大小近似等于小车及挡板受到的空气阻力.

汽车速度v/(m•s﹣15101520
弹簧测力计示数F/N0.10.51.11.9
(1)实验装置中用小车而不是木块,并将其放在表面平滑的木板上,目的是为了减小    对实验结果的影响.

(2)分析上表中的实验数据可知,物体运动速度越大,所受空气阻力越   

(3)实验完毕后,小华又进行了新的思考:空中下落的物体速度会增大,那么从足够高的高空下落的雨滴速度会不会一直增大,其所受的空气阻力会不会也一直增大?

在老师的指导下,小华知道了:若雨滴所受空气阻力小于重力,则雨滴下落速度继续增大;若下落雨滴所受空气阻力大于重力,则雨滴下落速度减小.

请你根据老师的上述指导和本实验结论并结合所学物理知识分析:一滴质量为5g的雨滴从高空下落时(假设在无风天气,雨滴下落高度足够大),所受到的最大阻力f=    N,此后雨滴做       运动(g=10N/kg).

(4)你认为运动物体受到的空气阻力大小还与                              有关.

单项选择题