问题 问答题

如图1所示是“验证动量守恒定律”实验装置,两小球半径相同,其质量之比为M:m=5:2,实验中,O点为斜槽末端重锤线的投影点,被碰小球停放在斜槽末端,小球落地点的平均位置如图2所示的P、M、N点,则表达动量守恒的式子应为______,代入数据后其结果应为动量______(填“守恒”或“不守恒”)

答案

两小球和B小球相撞后,被碰小球的速度增大,入射小球的速度减小,所以碰撞后入射小球的落地点距离O点最近,被碰小球离O点最远,则

P为碰前入射小球落点的平均位置,M为碰后入射小球的位置,N为碰后被碰小球的位置,设桌面离地面的高度为h,

碰撞前入射小球的速度v1=

.
OP
2h
g

碰撞后入射小球的速度

v2=

.
OM
2h
g

碰撞后被碰小球的速度v3=

.
ON
2h
g

若Mv1=mv3+Mv2则表明通过该实验验证了两球碰撞过程中动量守恒,

即:M

.
OP
=M
.
OM
+m
.
ON

带入数据得:M

.
OP
=
5
2
m×28=70m

M

.
OM
+m
.
ON
=
5
2
m×12+m×40=70m

所以动量守恒

故答案为:M

.
OP
=M
.
OM
+m
.
ON
;守恒

阅读理解

Singles Day (光棍节)falls on every November 11th, and as the name suggests, this holiday is one specially for people who are still living the single life. It’s surprising that China is the only country in the world that has set up a special day for singles to celebrate(庆祝) their lives. To find out more about this celebration, read on.

An old story goes that once there were four single men, leading very boring lives. None of them were married, or had lovers, or did anything exciting. They just sat around all day and played Mahjong(麻将).

One day they played Mahjong from 11 in the morning until 11 at night. During the game, no matter who won, the winning card was always the 'Sitiao' card. And that day happened to be November 11th. In order to remember the day, they called it Singles Day.

For breakfast on Singles Day, singles often eat four youtiao, which means the four "ones" in "11.11". Many singles also choose to say goodbye to their single lives on this day. So they take part in 'blind date' parties , trying to find someone they love and many people choose to marry on this day. Besides the meaning 'single', the four 'ones' of the date can also mean 'only one' as in 'the only one for me.' Some people will use this date and this meaning to tell their special someone that they are the only 'one' in their heart.

小题1:__________ first called November 11th Singles Day.

A.The Chinese government

B.People who have been married

C.Four people playing Marjong

D.People who don’t want to get married小题2:The Chinese meaning of the word “'blind date' parties” in this passage is “________”.

A.盲人聚会

B.相亲会

C.化妆舞会

D.盲人党派小题3:Singles often have ________ for breakfast on Singles Day.

A.some bread

B.noodles

C.4 youtiao

D.nothing小题4:Which of the following is NOT true according to the passage?

A.Singles Day is on November 11th.

B.Singles Day is celebrated by no countries but China.

C.Singles Day is for people who don’t have lovers.

D.To celebrate Singles Day, people play Marjong from 11 in the morninguntil 11 at night.

单项选择题 A1/A2型题