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一、对一个系统应用牛顿第二定律对系统应用牛顿第二定律,首先应确定系统的外力,并求出合力,再折合出Ma的矢量和,列出物理方程.或者把系统的合力投影到y轴和x轴上,求出y轴和x轴上的分力,再把加速度分别投影到y轴和x轴,由牛顿第二定律分别列出两轴的分量式. 相似文献
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<正>牛顿第二定律的内容是物体的加速度大小跟作用力成正比，跟物体的质量成反比，加速度的方向与作用力的方向相同．根据牛顿第二定律的内容可以得到关于力和加速度的同向性、瞬时性、因果性、同一性、独立性共五个性质，力和加速度的这五个性质说明力和加速度是不能割裂的、是共存亡的，掌握了力与加速度共存亡就可以玩转力和加速度，下面举两例说明． 相似文献
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贵刊03年8月号《牛顿第二定律的拓展公式及应用》一文中，王老师把运用牛顿第二定律整体方法解题的条件由加速度（大小和方向）相同拓展到加速度不同的问题中，本人也有同感．但须指明，其拓展公式∑F=m1a1＋m2a2＋…只能在各加速度的方向相同（或除某物体外其他物体的加速度为零）的条件下适用．对于加速度方向不同的情况，只要等效变换物体的受力情况，把牛顿第二定律进一步拓展，也能整体求解加速度方向不同的各种问题． 相似文献
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许致虎 《中学物理教学参考》2008,(3):30
当物体沿竖直方向有加速度时,由牛顿第二定律可知,物体对水平支持物的压力或对悬绳的拉力将小于或大于物体的重力,这就是失重或超重现象．当物体具有向下的加速度（或有向下的加速度分量）时,物体处于失重状态;当物体具有向上的加重度（或有向上的加速度分量）时,物体处于超重状态．利用失重和超重规律去定性分析判断有关题目,在很多情况下比应用牛顿第二定律要简单很多． 相似文献
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《中学生数理化(高中版)》2008,(10)
牛顿第二定律是最基本的物理定律之一,对于该定律的理解重点是掌握其"三性",即瞬时性、独立性和同向性.同学们在应用该定律时,常常分析不出合力的方向,故无法顺利地解决问题.实际上只要把握加速度 相似文献
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牛顿第二定律是研究力和运动关系的重要规律,归结起来,解题必须记住以下4项注意. 1牛顿第二定律的矢量性 矢量性是指加速度和合外力都是矢量,加速度的方向与合外力的方向总相同.根据加速度方向可以判断合外力的方向.反之,根据合外力方向也可判断加速度的方向. 相似文献
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牛顿第二定律F=mn揭示了加速度和力与质量之间的关系．作用在一个物体上的力和加速度之间时刻对应：①力和加速度方向相同;②力发生变化,加速度同步发生变化．在解决牛顿第二定律的相关问题时,我们要紧扣“力”这一要素,以物体受力分析为主线,根据物体受力变化情况准确划分运动过程． 相似文献
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牛顿第二定律是高中物理的一个重要定律．牛顿第二定律不仅对单个质点适用，对质点组或几个质点的组合体也适用．即使质点组中各质点的加速度不相等，牛顿第二定律一样适用．对质点组运用牛顿第二定律的表达式为：F合=m1a1＋m2a2＋m3a3＋…＋mnan此式也称作系统牛顿第二定律． 相似文献
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在牛顿第二定律的应用中，连接体是指几个物体或叠放在一起，或并排挤放在一起，或用细绳、细杆、弹簧联系在一起的物体组，在连接体内物体的加速度有相同和不相同两种情况，加速度相同情况可以用整体法、隔离法直接应用牛顿第二定律，较为简单．下面要讨论一下在加速度不同的情况下，如何应用牛顿第二定律的推广式来解决动力学问题． 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献