人用与水平方向成30°的斜向上拉力F=100N使M=10kg的箱子由静止开始沿光滑水平面运动．在2s内拉力做功为______，重力做功为______．
根据牛顿第二定律得：a=
=5Fcosθ m
m/s23
2s内的位移s=
at2=101 2
m3
所以在2s内拉力做功W=FScosθ=100×10×
=100×103 2
×3
=1500J3 2
因为物体在重力的方向上没有移动距离，所以重力不做功，即重力做功为0
故答案为：1500J；0
请认真阅读下列短文，并根据所读内容在文章后表格中的空格里填入一个最恰当的单词。（每空一个单词） There are two types of people in the world．Although they have equal degree of health and wealth and other comforts of life, one becomes happy, while the other becomes unhappy．This arises from the different ways in which they consider things, persons, events and the resulting effects upon their minds． People who are to be happy fix their attention on the convenience of things: the pleasant parts of conversation, the well prepared dishes, the goodness of the wine and the fine weather．They enjoy all the cheerful things．Those who are to be unhappy think and speak only of the opposite things．Therefore, they are continually dissatisfied．By their remarks, they sour the pleasure of society, offend（hurt） many people, and make themselves disagreeable everywhere．If this turn of mind was founded in nature, such unhappy persons would be the more to be pitied．The intention of criticizing and being disliked is perhaps taken up by imitation．It grows into a habit, unknown to its possessors．The habit may be strong, but it may be cured when those who have it realize its bad effects on their interests and tastes．I hope this little warning may be of service to them, and help them change this habit． Though in fact it is chiefly an act of the imagination, it has serious results in life since it brings on deep sorrow and bad luck．Those people offend many others; nobody loves them, and no one treats them with more than the most common politeness and respect．This frequently puts them in bad temper and draws them into arguments．If they aim at getting some advantages in social position or fortune, nobody wishes them success．Nor will anyone start a step or speak a word to favor their hopes．If they bring on themselves public objections, no one will defend or excuse them, and many will join to criticize their wrong doings．These should change this bad habit and be pleased with what is pleasing, without worrying needlessly about themselves and others．If they do not, it will be good for others to avoid any contact with them．Otherwise, it can be disagreeable and sometimes very inconvenient, especially when one becomes mixed up in their quarrels． Title: About Two Types of People
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