问题 填空题

在“验证机械能守恒定律”的实验中,重锤的质量应适当______(选填“大”或“小”)一些,实验结果总是动能的增加量略______(选填“大于”或“小于”)重力势能的减小量,原因是______的作用.

答案

重物带动纸带下落过程中,除了重力还受到空气阻力和纸带与打点计时器的摩擦力,从能量转化的角度,由于阻力做功,重力势能减小除了转化给了动能还有一部分转化给摩擦产生的内能,所以重力势能的减小量大于动能的增加量.

在实验中,重锤的质量应适当大些,那么阻力的作用就相对小了点.

故答案为:大,小于,空气对重锤的阻碍及纸带受到的摩擦

选择题
[ ]

A.生产力的不断发展

B.社会大变革的出现

C.频繁的争霸战争

D.学术的繁荣和思想的活跃

查看答案
阅读理解

阅读理解。

     EDGEWOOD-Every morning at Dixie Heights High School, customers pour into a special experiment:

the district's first coffee shop run mostly by students with special learning needs.

     Well before classes start, students and teachers order Lattes, Cappuccinos and Hot Chocolates. Then,

during the first period, teachers call in orders on their room phones, and students make deliveries.

     By closing time at 9.20 a.m., the shop usually sells 90 drinks.

     "Whoever made the chi tea, Ms. Schatzman says it was good," Christy McKinley, a second year student,

announced recently, after hanging up with the teacher.

     The shop is called the Dixie PIT, which stands for Power in Transition. Although some of the students

are not disabled, many are, and the PIT helps them prepare for life after high school.

     They learn not only how to run a coffee shop but also how to deal with their affairs. They keep a timecard

and receive paychecks, which they keep in check registers.

     Special-education teachers Kim Chevalier and Sue Casey introduced the Dixie PIT from a similar program

at Kennesaw Mountain High School in Georgia.

     Not that it was easy. Chevalier's first problem to overcome was product-related. Should schools be selling

coffee? What about sugar content?

     Kenton County Food Service Director Ginger Gray helped. She made sure all the drinks, which use non-fat

milk, fell within nutrition (营养) guidelines.

     The whole school has joined in to help.

     Teachers agreed to give up their lounge (休息室) in the mornings. Art students painted the name of the shop

on the wall. Business students designed the paychecks. The basketball team helped pay for cups.

1. What is the text mainly about? [ ]

A. A best-selling coffee.

B. A special educational program.

C. Government support for schools.

D. A new type of teacher-student relationship.

2. The Dixie PIT program was introduced in order to _____. [ ]

A. raise money for school affairs

B. do some research on nutrition

C. develop students' practical skills

D. supply teachers with drinks

3. How did Christy McKinley know Ms. Schatzman's opinion of the chi tea? [ ]

A. She met her in the shop.

B. She heard her telling others.

C. She talked to her on the phone.

D. She went to her office to deliver the tea.

4. We know from the text that Ginger Gray _____. [ ]

A. manages the Dixie P1T program in Kenton County

B. sees that the drinks meet health standards

C. teaches at Dixie Heights High School

D. owns the school's coffee shop