问题 问答题

[物理--选修3-5]

(1)下列关于光和原子的说法正确的是______.

A.发生光电效应时,产生的光电子的最大初动能与照射光强度无关

B.放射性物质发出的α、γ和β三种射线,是同一种原子核发生衰变时释放出的

C.所有核反应都会释放能量,

D.一群处于n=4能级的H原子发生跃迁辐射,最多可观测到6种不同频率的光子

E.α粒子散射实验揭示了原子具有核式结构

(2)如图所示,质量均为m的A、B两球,以轻质弹簧连接后置于光滑水平面上,开始弹簧处于自然状态.一质量为

1
4
m的泥丸P以水平速度v0沿A、B连线向A运动,击中A并粘合在一起,求以后的运动过程中弹簧的最大弹性势能.

答案

(1)A、发生光电效应时,根据爱因斯坦光电效应方程Ek=hγ-W知,产生的光电子的最大初动能与照射光的频率有关,与照射光的强度无关,故A正确.

B、放射性物质发出的α、γ和β三种射线,并不是同一种原子核发生衰变时释放出的,α射线是发生α衰变时产生的,β射线是发生β衰变产生的,而γ射线往往伴随着这两种衰变产生的,故B错误.

C、根据爱因斯坦质能方程E=mc2知,只有出现质量亏损的核反应才释放能量;相反,若质量增加,核反应将吸收能量.故C错误.

D、H原子的跃迁是随机的,一群处于n=4能级的H原子发生跃迁辐射,最多可观测到C

24
=6种不同频率的光子,故D正确.

E、α粒子散射实验揭示了原子具有核式结构,故E正确.

故选:ADE.

(2)设P与A球粘连在一起的共同速度为v1,由系统动量守恒有:

1
4
mv0=(m+
1
4
m)v1

当弹簧压至最短时,B与A的速度相等,设此速度为v2,由动量守恒有:

(m+

1
4
m)v1=(2m+
1
4
m)v2

由①②两式得:v1=

1
5
v0

v2=

1
9
v0

当弹簧压至最短时贮存在弹簧中的势能最大,设为EP

由能量守恒定律得:

EP=

1
2
(m+
1
4
m)
v21
-
1
2
(2m+
1
4
m)
v22

解得:EP=

1
90
m
v20

答:以后的运动过程中弹簧的最大弹性势能为

1
90
m
v20

选择题
阅读理解

Good sportsmanship occurs when teammates, opponents(对手), coaches, and officials treat each other with respect. Kids learn the basics of sportsmanship from the adults in their lives, especially their parents and their coaches. Kids who see adults behaving in a sportsmanlike way gradually come to understand that the real winners in sports are those who know how to keep on trying and to behave well - whether they win or lose a game.

Parents can help their kids understand that good sportsmanship includes both small gestures and heroic efforts. It starts with something as simple as shaking hands with opponents before a game and includes acknowledging good plays made by others and accepting bad calls gracefully. Showing good sportsmanship isn't always easy: It can be hard to congratulate the opposing team after losing a close or important game. But the kids who learn how to do it will benefit in many ways.

A child who bullies or laugh at others on the playing field isn't likely to change the behavior when in the classroom or in social situations. In the same way, a child who practices good sportsmanship is likely to carry the respect (尊重) and appreciation of other people into every other aspect of life

The best coaches - and parents - encourage their kids to play fair, to have fun, and to concentrate(专心于) on helping the team while improving their own skills.

小题1:The most important feature of good sportsmanship is ______.

A.respecting others.

B.concentrating on winning

C.improving one’s own skills.

D.beating the opposing team小题2:Which of the following is NOT the behavior of good sportsmanship?

A.Shaking hands with opponents

B.Playing on the field like heroes.

C.Praising good playing of others

D.Accepting unfriendly viewers’ opinions小题3: As a child with good sportsmanship, he / she will ______.

A.treat winning as the most important thing.

B.be proud of the success of his / her team

C.look down on others’ playing skills.

D.not get discouraged when defeated小题4:It can be inferred from the passage ______.

A.a child who bullies others can’t play well on the field.

B.the real winners are those who play with best skills.

C.a child with good sportsmanship behaves well in society

D.it is simple and easy to show one’s good sportsmanship