问题 问答题

在“验证力的平行四边形定则”实验中,需要将橡皮条的一端固定在水平木板上,先用一个弹簧秤拉橡皮条的另一端到某-点并记下该点的位置;再将橡皮条的另一端系两根细绳,细绳的另一端都有绳套,用两个弹簧秤分别勾住绳套,并互成角度地拉像皮条.

(1)某同学认为在此过程中必须注意以下几项:

A.两根细绳必须等长

B.橡皮条应与两绳夹角的平分线在同一直线上

C.在使用弹簧秤时要注意使弹簧秤与木板平面平行

D.在用两个弹簧秤同时拉细绳时要注意使两个弹簧秤的读数相等

E.在用两个弹簧秤同时拉细绳时必须将橡皮条的另一端拉到用一个弹簧秤拉时记下的位置

其中正确的是______.(填入相应的字母)

(2)本实验采用的科学方法是______

A.理想实验法       B.建立物理模型法    C、控制变量法       D.等效替代法.

答案

(1)本实验中我们只需使两个力的效果与一个力的效果相同即可,细绳的长度是否相等与本实验无关,合力不需要一定过两分力的角平分线,且两分力也不一定相等,故ABD错误;

但为了减小实验的误差,应要求用一个力拉和用两个力拉时的效果应相同,即必须将橡皮条拉至同一位置,故E正确;

为保证拉力的方向为在纸面上画出的方向,弹簧秤一定要与木板平行;故C正确;

故选CE.

 (2)本实验采用的是“等效替代法”,故ABC错误,D正确.

故选D.

单项选择题 A3/A4型题
阅读理解

Over 70 percent of the "double single-child couples" in China need help from their parents in taking care of their own kids, according to a recent survey.

"Women of China" magazine and a consulting company carried out a survey recently on young couples of the "single-child" generation, the Morning Post reports. The couples surveyed were around 29 and have been married for three years on average, with university education and monthly income of 4.000 yuan ($531). Among them, 43.5 percent have kids.

Results show that 71.9 percent of the young couples have help from their parents in taking care of their kids.

Grown up as the "single-child", the only child in a family since the family planning policy was adopted in 1979, this generation depends much on their parents.

The parents of the "single-child" generation focused more on their children's physical well-being rather than their attitudes and values, according to some psychologists.

The research also found that the "double single-child couples" follow a rather traditional value system.

Survey shows that 27.5 percent of them got married after dating for one to two years, 25.2 percent two to five years, and 20 percent didn't tie the knot until dating for five years. Also, 30 percent of the couples were schoolmates, while 43.8 percent were introduced by someone.

Since their marriage are based on enduring relationships, 65.2 percent of the husbands and 62.9 percent of the wives think that compromise(妥协)and tolerance(宽容)are necessary in their marriage. Meanwhile, 21.7 percent of the husbands and 37.1 percent of the wives support the idea that happiness is the key standard for a marriage.

小题1:The best title for the passage should be_______.

A.Mom and Dad, Take Care of My Kid Please

B.Double Single-child Couples

C.The Problem of the Single Child

D.A Recent Survey By Woman of China"小题2:Which of the following is NOT supported by the passage?

A.The majority of the "double single-child couples" in China depend much on their parents.

B.The parents of the “single-child” generation more care about their study and education.

C.One-fifth of the couples surveyed didn't get married until dating for five years.

D.All the couples surveyed have university education and 30 percent of them were schoolmates小题3:Which of the following descriptions about “double single-child couples” is True ?

A.They are single child in either family and independent of their parents

B.They are single child in either family and they are dependent on their parents

C.They have at least two children and can afford to support themselves

D.They, who were introduced by someone, follow a rather traditional value system小题4:According to the passage, we can learn that ______ is necessary in marriage.

A.wealth

B.health

C.understanding

D.education