问题 填空题

如图1所示是小徐同学做“探究做功与速度变化的关系”的实验装置.他将光电门固定在直轨道上的O点,用同一重物通过细线拉同一小车,每次小车都从不同位置由静止释放,各位

置A、B、C、D、E、F、G(图中只标出了O、G)离O点的距离d分别为8cm、16cm、24cm、32cm、40cm、48cm,56cm.

(1)该实验是否需要测量重物的重力______(填“需要”或“不需要”);

(2)该实验是否必须平衡摩擦力?______(填“是”或“否”);

(3)为了探究做功与速度变化的规律,依次得到的实验数据记录如表所示.请选取其中最合适的两行数据在答题卷的方格纸内描点作图.

(4)从图2的图象得到的直接结论是______,从而间接得到做功与物体速度变化的规律是______.

实验次数1234567
d/×10-2m8.0016.0024.0032.0040.0048.0056.00
v/(m/s)0.490.690.850.991.091.211.50
v2/(m/s)20.240.480.720.981.191.462.25
v
/(m/s)
3
2
0.700.830.921.001.041.101.23

答案

(1)该实验中,根据W=Fs,F=ma和s=

v2t
-
v20
2a
,可得,Fs=
1
2
m
v2t
-
1
2
m
v20
,即外力做功与物体的质量无关,实验不需要测量物体的质量(重力);

(2)该实验中已经测量了物体的位移与速度,来探究合外力与物体的速度的变化关系,所以是否存在摩擦力对该实验没有影响.故不需要平衡摩擦力.

(3)根据表格中记录的数据可得,物体的位移d与物体的速度、以及速度的平方根都不存在正比例的关系,与速度的平方接近正比例关系,所以可选择v2为坐标系的纵坐标.将表格中的数据在d-v2坐标系中描点连线如图.

(4)从图2的图象得到的直接结论是d与v2成正比;从而间接得到做功与物体速度变化的规律是合外力做功与v2成正比.

故答案为:(1)不需要;(2)否;(3)如图;(4)d与v2成正比,合外力做功与v2成正比.

阅读理解

"Beating is a sign of affection, cursing (骂)is a sign of love."

Many may not expect to hear the words of the old Chinese saying in these modern times—with parents wealthier and better educated than they have ever been-but experts say they still ring true.

Today, it seems, Chinese parents are more likely to send their children to pre-college military academies in the United States in the hope that some tough love will pave the way tosuccess.

"Good education doesn't mean letting your child enjoy privileges, especially our boys," said Song Wenming, an entrepreneur(企业家)in Jinhua, East China's Zhejiang province." They should be raised in tough conditions to know what to fight for in the future."

In August, Song sent his 17-year-old son to Valley Forge Military Academy (VFMA) in Pennsylvania. And he is far from alone, even though it takes a lot of money - around $48,000 per year —to send a child to a strict military school.

Statistics shows that an increasing number of Chinese students have been registering with such academies.

A few years ago, there were no Chinese students at Valley Forge. Today, there are 28."All of the Chinese students at Valley Forge came from wealthy families, some of them were spoiled," said Jennifer Myers, director of marketing and communications at the school.

Song's only son, Song Siyu, had a rocky start during his first six weeks at the school. The teenager said he went to the school voluntarily but did not expect it to be as difficult.

Now, three months later, he has perfected the art of taking a bath in 35 seconds, finishing a meal without looking at his food, and making his bed with precision. He can even take criticism, no matter how unreasonable.

"The training is hard but I know it is good for self-development of individuals," said Song Siyu.'The endless training and scolding are just ways to build up our character, they are not personal."

But his enthusiasm is not universal. Ten of the 13 Chinese students who joined the academy this year have transferred to other schools.

But for those who stick with it, there is a reward for all the hard work.

小题1:From the second paragraph, we can know the old Chinese saying _____.

A.is out of date in modern times.

B.is disagreed by rich parents.

C.is still worth trusting

D.is deeply believed by better educated parent.小题2:The underlined sentence means that _____

A.Song sent his only son to military school, so he feels lonely.

B.Song is the only one who sends his child t to military school.

C.There are other people sending their children to military school besides Song.

D.The fee of the military school is so high that only Song can afford it.小题3:Song Siyu got some achievements in the military school except _____.

A.taking a bath in a short time

B.having his meal with his eyes closed

C.taking unreasonable criticism

D.improving his character小题4:How many Chinese students are there at Valley Forge before this year?

A.10

B.13

C.15

D.25小题5:Which of the following can be inferred from the passage?

A.   It's likely that more and more Chinese students will attend VFMA.

B.    Most Chinese parents approve of educating their children by beating and cursing nowadays.

C.   Song Siyu had no difficulty in adjusting to the life at VFMA.

D.   Most Chinese students support the way of education at VFMA.

单项选择题