问题 问答题

在用单摆测重力加速度的实验中:

(1)应注意,实验时必须控制摆角在______内,并且要让单摆在______内摆动.

(2)测量单摆周期时,等单摆自由振动几次之后,从摆球经过______位置时开始计时,因为这时摆球的速度______,可以减少误差.

(3)某同学测出不同摆长时对应的周期T,作出L-T2图线,如图所示,再利用图线上任意两点A、B的坐标(x1,y1)、(x2,y2),可求得g=______.

(4)若该同学测摆长时漏加了小球半径,而其他测量、计算均无误,也不考虑实验误差,则以上方法得的g值和真实值相比是______的(“偏大”“偏小”或“不变”).

答案

(1)单摆模型是一种理想化的模型,只有在摆动角度小于5°(或10°)的范围内,其运动才近似为简谐运动,同时要注意不能做圆锥摆运动

故答案为:5°或10°,同一竖直平面.

(2)测量周期要尽量减小偶然误差,应该从摆球经过最低位置时开始计时,因为这时摆球的速度最大可以减少误差

故答案为:最低,最大.

(3)由周期公式T=2π

L
g
,可得

L=

g
4π2
T2

代入数据可得

g=4π2

y2-y1
x2-x1

故答案为4π2

y2-y1
x2-x1

(4)通过第(3)问的结论可以知道,漏加了小球半径后(y2-y1)不变,故不影响最后结果

故答案为:不变.

阅读理解

阅读下列短文,从每个小题所给的选项中选出最佳答案。

     We moved to a new area when our son was in Grade  Five. Before we moved, we took him to

spend half a day at his new school. There he saw his new classmates and teachers. He enjoyed the

visit. During the almost 150-kilometer drive home, he told us that he had told some of the students

the date when we would move there. And he had also invited them to visit us. The moving day, a

Saturday, was a busy day. But we arrived at our new house at noon. About an hour later, kids

began to come and soon one of them invited our son to his house to play for the afternoon. By

the time he returned, he knew where most of the kids lived and all of their family histories. On

Monday morning,the door bell rang just before the time he would leave for school. Then it rang

again and again. By the time he was ready, we had eight young boys waiting to walk to school with

him on his first day. They all lived near us. I asked them if their parents had sent them. The answers

surprised and pleased me, "No, we just came so that we would have people to walk with. "and "It is

the right thing to do. " The startings of lasting (持续的) friendships were formed (形成) that day.

We have lived here nearly six years and the same group of kids still plays together, goes to parties

on weekends together, and surfs together.

      I still get thinking how welcoming and kind those kids were. And how lucky my son is to have

them as friends!

1. Before the family moved to the new area, the son was taken to his new school  _____. [ ]

A. to invite the teachers to visit them

B. to play with his classmates

C. to see if the school was far

D. to get to know it

2. What did the son know about other kids after they played for the afternoon?[     ]

A. Their living places and family histories.

B. Their family stories and their life.

C. Their school life and family histories.

D. Their living places and family members.

3. In the story, the son went to school _____ on his first day. [ ]

A. in his father's car

B. on a school bus

C. on foot with other kids

D. in another kid's car

4. Which of the following is right according to the story? [ ]

A. The family moved to the new house on Saturday afternoon.

B. The kids visited the house before the family arrived.

C. The son knew the kids well before he got there.

D. The son was invited to play in a kid's house later that afternoon.

5. The passage shows us that _____.[ ]

A. it's easy to move to a new place

B. it's kind of people to help a new comer

C. it's difficult to make new friends

D. it's better to live in the same place

单项选择题