问题 填空题

如图为“用DIS(位移传感器、数据采集器、计算机)研究加速度和力的关系”的实验装置。

(1)在该实验中必须采用          ,应保持小车的总质量不变,用钩码所受的重力作为小车所受外力,用DIS测小车的加速度。

(2)改变所挂钩码的数量,多次重复测量。在某次实验中根据测得的多组数据可画出a-F关系图线(如图所示)。分析此图线的AB段明显偏离直线,造成此误差的主要原因是            

A.小车与轨道之间存在摩擦

B.导轨保持了水平状态

C.所挂钩码的总质量太大

D.所用小车的质量太大

答案

控制变量法     C  

题目分析:(1)试验中的变量由三个,只有让其中一个不变,才能研究另外两个量的关系,这种方法叫控制变量法。

(2)本实验要求小车的质量远远大于钩码的质量,否则就会出现图线反映的情况;故选C

点评:中等难度。 控制变量法是研究多个物理量之间关系的一种常用方法,即在多因素实验中,先控制一些量不变,依次研究某一些因素的影响,这是一种重要的科学实验方法,在以后的学习中,我们会经常用到这种方法,同学们要仔细体会这一方法的重要性。

阅读理解

阅读理解。

                                                               Body and Food

     Your body, which has close relations with the food you eat, is the most important thing you own, so it

needs proper treatment and proper nourishment (营养).The old saying "An apple a day keeps the doctor away"is not as silly as some people think. The body needs fruit and vegetables because they contain

vitamin C. Many people take extra vitamins in pill form, believing that these will make them healthy.

     But a good diet is made up of nourishing food and this gives all the vitamins you need. The body

doesn't need or use extra vitamins, so why waste money on them?

     In the modern western world, many people are too busy to bother about eating properly. They throw

anything into their stomachs, eating hurriedly and carelessly. The list of illnesses caused or made worse by bad eating habits is frightening,

1. "Your body has close relations with the food you eat." It really means that ______.

A. all kinds of food you eat can be made into your body

B. your body is made up of the food you eat

C. what you eat has great effect on your health

D. the more you eat, the fitter you will feel

2. The old saying referred to in the, passage tells us that ______.

A. eating apples regularly does lots of good to our health

B. the apple is the best among all kinds of fruits

C. apples can take the place of doctors

D. an apple is a sure cure for illness

3. In the second paragraph, the writer tries to let us know ______.

A. our bodies need food or we can't live

B. often eating apples is a good habit

C. taking extra vitamin pills is completely useless

D. a good diet is of great importance for our health

4. In the modern western countries ______.

A. people don't want to pay more attention to their eating

B. lots of people's illnesses are caused or made worse by bad eating habits

C. people throw everything into their stomachs without chewing

D. people are only too busy to cook meals for themselves

5. From the passage we can draw a conclusion that if we want to keep healthy,we should ______.

A. only eat an apple a day

B. eat properly

C. take as many vitamin pills as possible

D. throw something into our stomachs slowly and carefully

单项选择题