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物质是由大量分子组成的,分子直径的数量级一般是多少?能说明物体内分子都在永不停息地做无规则运动的实验事实有什么例子?在两分子间的距离由r0(此时分子间的引力和斥力相互平衡,分子作用力为零)逐渐增大的过程中,分子力的变化情况是?

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解答: 分子直径数量级一般是1010m;

扩散现象说明分子在永不停息地做无规则运动;

当分子间距大于平衡位置时,若间距增大,则分子引力与斥力都在减小,但斥力减小得快,所以体现为引力,则引力越来越大,随着间距增大一定值时,引力与斥力都变小,所以分子力也变小,故分子力先增大后减小.

故答案为:1010;扩散;先增大后减小.

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    The uninvolved dad, turning up his nose at diapering(换尿布) and too busy to bathe, dress and play with his kids, is mostly a myth(神话) , a big government survey suggests. Most American fathers say they are heavily involved in hands-on parenting, the researchers found.

    The results are encouraging and important " because others have found the more involved dads  are, the better the outcomes for their children. " said researcher Jo Jones of the National Center for Health Statistics, part of the Centers for Disease Control Prevention. She co-authored the report released Friday.

    "Times have changed," said Robert Loftus, 34, of Yonkers, NY. He quit a six-figure sales job a year ago to care for his two young children while his wife works full time. "We are trying to rethink our priorities (优先考虑的事) and family seem to be NO.1 priority while in the past maybe people were more focused on career. "

    The study involved nearly 4.000 fathers who were interviewed in person between 2009 and 2013.

◇ Key findings among fathers living with children younger than 5 :

*9 in 10 bathed, diapered, helped them use the toilet or get dressed at least several times weekly .

* Even higher numbers played with them and ate meals with them that often

* Almost 2 0ut of 3 read to them at least several times weekly.

◇Among dads living with kids aged 5-18.

* More than 9 0ut of 10 ate meals with them at least several times weekly and talked with them about what happened during the kids' day that often.

* Almost 2 0ut of 3 helped with homework several times weekly.

* About half took their kids to or from activities that often.

    Dr. David Hill, a Wilmington, N. C. pediatrician (儿科医生) said the survey reflects what he's seen among his patients' fathers. Increasingly, fathers rather than mothers take their kids to the doctor. Some "are anxious about changing a diaper, " he said.

    Census(调查) numbers show that there were almost 190,000 stay-at-home dads nationwide last year versus 93,000 in 2010. Loftus, the New York stay-at-home dad, said, "I feel fortunate to be able to be such a hands-on father.  I'm doing the most significant occupation in the world. "