问题
单项选择题
大小分别为5N和10N的两个力，同时作用在同一直线上，其合力的大小( )。
A．只能是15N
B．只能是5N
C．大于5N，小于15N
D．可能5N，也可能15N
答案
参考答案：D
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大小分别为5N和10N的两个力，同时作用在同一直线上，其合力的大小( )。
A．只能是15N
B．只能是5N
C．大于5N，小于15N
D．可能5N，也可能15N
参考答案：D
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| Profits of Praise Are we too quick to blame and slow to praise? It seems we are. Praise is like sunlight to the human spirit; we cannot flower and grow without it. And yet, while most of us are only too ready to apply to others the cold wind of criticism, we are somehow unwilling to give others the warm sunshine of praise. It's strange how mean we are about praising. Perhaps it's because few of us know how to accept praise gracefully. Instead, we are embarrassed and shrug off the words we are really so glad to hear. Because of this defensive reaction, direct compliments are surprisingly difficult to give. That is why some of the most valued pats on the back are those which come to us indirectly, in a letter or passed on by a friend. Do you ever go into a house and say, "What a tidy room!" Hardly anybody does. That's why housework is considered such a boring job. Shakespeare said, "Our praises are our wages." Since so often praise is the only wage a housewife receives, surely she is well worth praising. Mothers know naturally that for children an ounce of praise is worth a pound of scolding. Still, we're not always aware of children's small achievements and we seldom apply the rule. One day I was criticizing my children for quarreling. "Can you never play peacefully?" I shouted. Susanna looked at me, confused. "Of course we can," she said. "But you don't notice us when we do." Teachers agree about the value of praise. "I believe that a student knows when he has handed in something above his usual standard," writes a teacher, "and that he waits and is hungry for a brief comment in the margin to show him that the teacher is aware of it, too." Behavioral scientists have done countless experiments to prove that any human being have a tendency to repeat an act which has been immediately followed by a pleasant result. In one such experiment, a number of schoolchildren were divided into three groups and given arithmetic tests daily for five days. One group was consistently praised for its previous performance; another group was criticized; the third was ignored. Not surprisingly, those who were praised improved dramatically. Those who were criticized improved also, bus not so much. And the scores of the children who were ignored hardly improved at all. Interestingly the brightest children were helped just as much by criticism as by praise, but the less able children reacted badly to criticism, needed praise the most. Yet the latter are the very youngsters who, in most schools, fail to get the pat on the back. To give praise costs the giver nothing but a moment's thought and a moment's effort-perhaps a quick phone call to pass on your praise, or five minutes spent writing an appreciative letter. It is such a small investment-and yet consider the results it may produce. "I can live for two months on a good compliment," said Mark Twain. So, let's be alert to the small excellences around us-and comment on them. We will not only bring joy into other people's lives, but also, very often, added happiness into our own. Title: Profits of Praise
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