问题 问答题

在“用单摆测定重力加速度”的实验中:

(1)老师提供了体积相同且均为实心的木球、铝球和钢球,你认为应选择______球用来制作单摆进行实验.

(2)若在某次实验中,测得单摆摆长为l、单摆完成n次全振动的时间为t,则利用上述测量量和常数求重力加速度g的表达式为g=______.

答案

(1)因为阻力与钢球的重力比较,可以忽略,所以选钢球.

(2)单摆完成n次全振动的时间为t,所以T=

t
n
.根据T=
L
g
,g=
4π2l
T2
=
4π2n2l
t2

故本题答案为:钢球,

4π2n2l
t2

阅读理解

阅读理解。

      Parents whose children show a special interest in a sport feel very difficult to make a decision about their

children's careers. Should they allow their children to train to become top sports men and women? For many

children it means starting schoolwork very young, and going out with friends and other interests have to take

a second place. It's very difficult to explain to a young child why he or she has to train five hours a day, even

at the weekend, when most of his or her friends are playing.

      Another problem is of course money. In many countries money for training is available from government

for the very best young sportsmen and women. If this help can not be given, it means that it is the parents

who have to find the time and the money to support their child's development and sports clothes, transport to

competitions, special equipment, etc. Can all be very expensive?

      Many parents are worried that it is dangerous to start serious training in a sport at an early age. Some

doctors agree that young muscles may be damaged by training before they are properly developed. Professional

(专业的) trainers, however, believe that it is only by training young that you can reach the top as a successful

sports person. It is clear that very few people do reach the top, and both parents and children should be

prepared for failure even after many years of training.

1. This article is most probably taken from ____. [ ]

A. a letter

B. an advertisement

C. a personal diary

D. a newspaper article

2. According to the passage, parents whose children show a special interest in sport ____. [ ]

A. feel uncertain if they should let their children train to be sports men or women.

B. try to get financial(财政的) support from the government for their children's training.

C. have to get medical advice from doctors about training methods.

D. prefer their children to be trained as young as possible.

3. Which of the following statements is NOT true? [ ]

A. By starting young, you won't have much time for your schoolwork.

B. Early training may damage your muscles.

C. Most children may become professional sports men after a long period of training.

D. It's very expensive for parents to support their child's development in sports.

4. The phrase "to take a second place" means ____. [ ]

A. to repeat the activities some other day

B. to become less important

C. of all the things, they are the most important

D. to happen again

5. ____ can become the best players after many years of training. [ ]

A. Most people

B. Some people

C. Hardly any people

D. No people

单项选择题