问题 选择题

如图所示,一轻弹簧一端固定于O点,另一端系一重物,将重物从与悬点O在同一水平面且弹簧保持原长的A点无初速地释放,让它自由摆下,不计空气阻力,在重物由A点摆向最低点B的过程中

A.重力做正功,弹力不做功

B.重力势能减少,弹性势能增加

C.若用与弹簧原长相等的细绳代替弹簧后,重力做正功,弹力不做功

D.若用与弹簧原长相等的细绳代替弹簧后,重力做功不变,弹力做功发生变化

答案

BC

重物由A点摆向最低点B的过程中,重力做正功,重力势能减小,弹簧伸长,则弹力做负功,弹性势能增加,A错误、B正确;若用与弹簧原长相等的细绳代替弹簧,由于细绳不伸长,弹力不做功,重力仍做正功,但由于下降的距离比原来小,故重力做功发生变化,C正确,D错误。

阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。

选项中有两项为多余选项。

    Women's roles have changed throughout the world in recent years, but nowhere so obviously as

in America .1________ .In many American homes today ,the husband still carries on his traditional

role of breadwinner ,while his homemaker wife is in charge of the home and child-raising. But it is more

and more common to find that the children are left in day -care centers or nursery schools while both

parents work 2___________. At home, household duties are shared in varying degrees by all family

members .It is not unusual to find father cooking dinner, cleaning the living room or changing the baby

.3 ______.Children have responsibilities, too .One of the goals of the Women's Liberation Movement

has been to have both men and women share in childcare, housework and financial responsibility.

4 _ ____.

   The high cost of living has made it necessary for many women to have jobs outside the home ,but

women often choose to have jobs in order to use their skills and education or to seek a more fulfilling

and interesting life .Many American women enjoy the independence that an outside job and the salary

give men and even some women-sometimes are not for women working outside the home ,and in some

cases ,a woman might be paid less than a man who performs the same job .5__  __.

A. As the roles of women have changed, so have men's

B. The woman may earn as much or more money than her husband

C. Mother might be outside mowing the lawn or washing the car

D. Today many American women will not marry a man who is not willing to share equally in household responsibilities

E. American women, however, have met challenges(挑战)since pioneer days ,and they continue to work for true equality

F. women didn't play an important role in the past

G. women in America were not happy in the past

判断题