问题 问答题

(1)经多长时间两球发生第一次碰撞?碰撞前小球A的速度为多大?

(2)在以后的各次碰撞中,相邻两次碰撞间隔的时间是否相等(如相等,为多少;如不等,说理由)?

(3)从加上电场起计时,经多长时间小球A以多大的速度与小球B发生第3次碰撞?

答案

(1),

(2)

(3)

(1)小球A从开始运动至与B球碰前有:

               

由上三式可得:,(每式1分,共5分)

(2)在每次碰撞过程中有:

由上可得:,,

即每次碰后A、B两球交换速度,绘出它们的图象如下

可见:以后的相邻两次碰撞间隔的时间相等,为

(3)由图可直接得到:从加上电场起计时,经时间

小球A与小球B发生第三次碰撞,此时球A速度为

阅读理解

阅读理解。

     Who do you think was the most important woman of the past 100 years?

     Jane Addams (1860 - 1935)

     Addams helped the poor and worked for peace. She created shelters, education opportunities and

services for people in need. In 1931, Addams became the first American woman to win the Noble

Peace Price.

     Rachel Carson (1907 - 1964)

     Rachel Carson was born in the rural river town of Springdale, Pennsylvania in America. The popular

1962 book "Silent Spring" by Rachel Carson made people realize the dangers and the harmful effects

(影响) of pollution on humans and on the world's lakes and oceans.

     Angela Merkel (1954 - )

     In 2005, Germans chose Angela Merkel as their first woman head of the country. She had been a

scientist in the past. As Germany's leader, she has had an effect on the whole world.

     Sandra Day O' Connor (1930 - )

     When Sandra Day O' Connor finished her class at Stanford Law School, in 1952, she could not find

work because she was a woman. However, she became the first woman to join the U.S. Supreme Court (最高法院) in 1981 after years of hard work.

     Margaret Thatcher (1925 - )

     In 1979, Margaret Thatcher became Britain's first woman Prime Minister (首相). She served until

1990, which made her the first British leader to serve three terms in a row. Because of her high standards

and strong will, people called her Britain's Iron Lady.

     Marie Curie (1867 - 1934)

     Polish-born scientist Marie Curie discovered that some types of metal give off energy called radiation (辐射能). Her research led to new medical treatments and arms. She received the Nobel Prize in physics

in 1903 and in Chemistry in 1911.

1. Who once won the Nobel Price?

A. Jane Addams and Marie Curie

B. Jane Addams and Margaret Thatcher

C. Marie Curie and Angela Merkel

D. Marie Curie and Rachel Carson

2. We can infer from the text that Rachel Carson worked to _______.

A. help the poor

B. spread geographic knowledge

C. protect the environment

D. protect the rights of women

3. What do Angela Merkel and Margaret Thatcher have in common?

A. Both of them were scientists before coming to power.

B. Both of them are the first woman head of their country.

C. Both of them are famous for being strict.

D. Both of them have worked for three terms.

4. Who once failed to find a job?

A. Jane Addams.

B. Sandra Day O' Connor

C. Rachel Carson

D. Margaret Thatcher

单项选择题