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光滑水平面上叠放着两个质量分为m1m2（m1噢 有两个力,一个3N,一个5N,则他们的合理大小是?A 可能是3N B 可能是7N C 可能是5N D 可能是12N选哪个?麻烦讲清楚, 物体A在水平力F（水平向右）的作用下静止在竖直墙壁上,当水平力减小为F/2时,物体A恰好沿竖直墙壁匀速下滑,此时物体A所受的大小为：我知道这道题的答案是和原来一样,物体A收到的力F这个 一个人利用滑轮,坐在吊桶装置上升.要自己慢慢匀速上升,他需要用多大力拉绳?可能我说的有点模糊,这是图,http://books.google.cn/books?id=sWDYRDeFeh4C&pg=PA22&lpg=PA22&dq=%E8%87%AA%E5%B7%B1%E6%85%A2%E6%85%A2%E5%8C%8 求一篇作文《那些你不知道的事》 别写恋爱的事 14岁孩子不愿上学要去南方打工,谁给出出主意.大人怎么说都不行. 求一篇800字初中作文,有关青春的,明天交,急还有很多作业,来不及想 家长为什么要孩子好好读书? 未来的家乡 初中作文700字 急求一篇600~700字初中作文:责任的美丽不要太长,600~700/800字就可以,美点的- -不好意思,忘了说了,要的是记叙问,不要议论的 - -那篇什么英国王子的就~不要了 关于波的,不过是英语的~1.A source of sound waves of frequency 1.0 kHz is traveling through the air at 0.50 times the speed of sound.(a) Find the frequency of the sound received by a stationary observer if the source moves towards her.(b) Rep 1.A dolphin can leap several meters above the ocean's surface.Why doesn't gravity stop the dolphin from leaving the water?2.why do loose objects on the dashboard slide to the right when the car turns suddenly to the left? 英语介绍自己我是个男孩 13岁50词 读书笔记应该怎么写?有没有什么格式?老师让他写读书笔记, 为了提高他的阅读兴趣和阅读量,我不知道叫他读什么课外书,请哪位朋友给我推荐一下 大学里的物理题目 in english!A stone is released from a balloon that is descending at a constant speed of 10 m/s. Neglectingair resistance, after 20 s the speed of the stone is:2160 m/s176 求篇以“比”为话题的高中八百字作文. 一个简单的化学题（in english)Which mass of oxygen combines with 12g of magnesium?A 4gB 8gC 16gD 32g说明原因.C 请以《明天》为话题写一篇作文,600字好的加··· An object with an initial velocity of 4m/s moves along a straight axis uder constant acceleration.Three seconds later ,its velocity is 14m/s.How far did it travel during this time? 有没有数学书目录什么的?照下来我想看看. 请看下题.数学书本上有的温州到北京路程为400千米,车速100千米每小时.到杭州18点25出发.到了杭州并不能马上上火车,市内交通和监票进站要花去40~50分钟.我最迟什么时候从温州出发才一定赶 以“放眼未来”为话题,写一篇八百字以上的作文 一道英文物理题A 4kg body is placed on horizontal ground.The coefficient of dynamic friction between the body and the ground is 0,2.The object is acted upon by a force of 30 N that encloses an angles of 20 whith horizontal.Find the friction for 一道英文的物理题Which of the following is a torque expression?A. 􀀁 = maB. 􀀂 = m􀀁vC. 􀀂 = vsinA􀀁D. 􀀂 = FsinA*d翻译一下,还有答案是哪个? 一道物理英文题The speed of a bullet as it travels down the barrel of a rifle toward the opening is given by v = (–5.00 × 107)t2 + (3.00 × 105)t,where v is in meters per second and t is in seconds.The acceleration of the bullet just as it l 一道物理题（英文的）Maximum power transfer to the load RL occurs when its value is （30）最好是用Thevenin's Theorem,好像叫戴伟宁定律当RL=Rth时,P最大,好像是要把电源断路,然后求Rth,我不明白那个Rth是怎 还有一道英文物理题an air-filled ballon floating on the surface of the water is in a region where the currrent in the water has a velocity Vc and the wind has a velocity Vw.the actual velocity of the ballon is given by:A.Vc+VwB.Vc-VwC.Vw-VcD. 我儿子今年上初一了,可是他的数学却学的一点也不好,题也没少做,可是你给他讲也不会,为什么呢,难道数学真的这么难吗有谁帮帮我,到底怎么办,才能学会谢谢急! 儿子现在读初一的快班,但好多数学拓展题都不会,怎么办 孩子读初一了,数学反应慢,怎么办? 求《说普通话的好处》 写一篇论文1000字以上,明天要交!