问题 问答题

如图所示,在光滑水平面上,质量为m的小球B连接着一个轻质弹簧,弹簧与小球均处于静止状态.质量为2m的小球A以大小为v0的水平速度向右运动,接触弹簧后逐渐压缩弹簧并使B运动,经过一段时间,A与弹簧分离.

(1)当弹簧压缩至最短时,弹簧的弹性势能EP为多大?

(2)若开始时,在B球的右侧某位置固定一块挡板,在A与弹簧未分离前使B球与挡板发生碰撞,并在碰撞后立即将挡板撤走.设B球与挡板碰撞时间极短,碰后B球的速度大小不变,但方向与原来相反.欲使此后弹簧被压缩到最短时弹簧的弹性势能能达到第(1)问中EP的2.5倍,必须使两球在速度达到多大时与挡板发生碰撞?

答案

(1)(2)                

(1)弹簧压缩至最短时,A、B速度均

v,选取向右为正,根据动量守恒定律,有:                                3分

根据机械能守恒定律,有:

                    3分

(2)设B球与挡板碰撞时,A球速度为v1、B球速度为v2(均向右)

根据动量守恒定律:   ——①         2分

此时弹簧弹性势            3分

则B球与挡板刚碰后:A球速度为v1、 B球速度为-v2(向左),此后

弹簧压缩至最短时共同速度为v3,则:

    ——②                          2分

此时弹簧弹性势能

              2分

由题意:              得——③ 3分

由①②③式可得:            2分

单项选择题 A1/A2型题
阅读理解

阅读理解。

                                                                                                                              LINDA MAYNARD

                                                                                                                             11 Windrift

                                                                                                                             Circle Methuen, MA

                                                                                                                             978-555-4539

     JOB OBJECTIVE

      Seek special education, primary school, or middle school math teaching position.

      EDUCATION

      Rivier College, Nashua, NH

      Bachelor of Arts in Education-May, 2006

      Major: Elementary Education

      Have successfully completed PRAXIS I and PRAXIS II. Meet highly qualified testing requirements for

Massachusetts and New Hampshire.

      TEACHING EXPERIENCE

      November, 2005-January, 2006

      Wilkins Elementary School, Amherst, NH

      Student Teacher

     · Developed and completed student-centered lessons in all subject areas for various groups of fifth grade

special and regular education students.

     ·Adapted lessons to meet students' needs by reviewing their backgrounds and learning needs through

IEPs.   

     ·Communicated with parents on a regular basis via newsletters, daily or weekly progress reports, phone

calls, and email, resulting in increased parental participation at home.

      September, 2005-November, 2005

      Charlotte Avenue Elementary School, Nashua, NH

      Student Teacher

     ·Taught reading and writing through Language Experience Approach methods.

     ·Introduced a Writer's Workshop appropriate for first grade students to help them to develop their writing

skills. 

     ·Developed learning stations in reading and science, enabling students to be more independent learners. 

      Spring, 2005

      Wilkins Elementary School, Amherst, NH

      Designed and taught a unit on Insects and Spiders, based on New Hampshire Standards to 23

self-contained, third and fourth grade students with disabilities.

      Fall, 2004

      Amherst Street Elementary School, Nashua, NH 

      Taught a class of 24 third grade students with a wide range of abilities.

      ADDITIONAL EXPERIENCE

     ·After-School Aid, Amherst School District, Amherst, NH (2004-2005)

     ·Summer Camp advisor, YMCA, Nashua, NH (Summers, 2002 and 2003)

     ·Big Brother / Big Sister Volunteer, Nashua, NH (2002-2005)

1. What kind of job does Linda want to get? [ ]

A. A Big Brother / Big Sister Volunteer.

B. A middle school math teacher.

C. A special education advisor.

D. A summer camp advisor.

2. Linda has worked for the following schools EXCEPT ______. [ ]

A. Rivier College, Nashua, NH

B. Wilkins Elementary School, Amherst, NH

C. Charlotte Avenue Elementary School, Nashua, NH

D. Amherst Street Elementary School, Nashua, NH

3. What can we know about Linda according to the passage? [ ]

A. She was merely interested in developing student's math abilities.

B. She was not active in participating in after-school activities.

C. She is permitted to teach in any high school of New York.

D. She has plenty of experience in teaching.

4. Which of the following is NOT included in the ways Linda used to communicate with the students' parents? [ ]

A. Newsletters.

B. Phone calls.

C. Face-to-face talks.

D. Daily or weekly progress reports.