"Congratulations, Mr. Jones, it’s a girl. "
Fatherhood is going to have a different meaning and bring forth a different answer from every man who hears these words. Some feel proud when they receive the news, while others worry, wondering whether they will be good fathers. Although there are some men who like children and may have had considerable experience with them, others do not particularly care for children and spend little time with them. Many fathers and mothers have been planning and looking forward to children for some time. For other couples, pregnancy was an accident that both husband and wife have accepted willingly or unwillingly.
Whatever the reaction to the birth of a child, it is obvious that the change from the role of husband to that of father is a difficult task. Yet, unfortunately, few attempts have been made to educate fathers in this re-socialization process. Although many good books have been written about American mothers, only recently have some books discussed the role of a father.
It is argued by some writers that the transition to the father’s role, although difficult, is not nearly as great as the transition the wife must make to the mother’s role. The mother’s role seems to require a complete transformation of daily routine and adaptation to a new life, on the other hand, the father’s role is less demanding and immediate. However, even though we have mentioned the fact that growing numbers of women are working outside the home, the father is still thought by many as the breadwinner in the household.
Some writers argue that with respect to the change of roles, fathers, compared with mothers,（）
A. have to do more in the household
B. have to make more difficult adaptations
C. have an easier job to do
D. can usually do a better job
关系
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（其中c为真空中的光速，h为普朗克常量）（2）如图所示，A为有光滑曲面的固定轨道，轨道底端的切线方向是水平的。质量M＝40 kg的小车B静止于轨道右侧的水平地面上，其上表面与轨道底端在同一水平面上。一个质量m＝20 kg的物体C以2.0 m/s的初速度从轨道顶端滑下，冲上小车B后经一段时间与小车B相对静止并一起运动。若轨道顶端与底端的高度差h＝1.6 m，物体与小车间的动摩擦因数μ＝0.40，小车与水平地面间的摩擦忽略不计，取重力加速度g＝10 m/s2，求：