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一道高中物理题,希望给出答案和讲解如图所示,质量为m的运动员站在质量为m/2的均匀长板AB的中点,板位于水平地面上,可绕通过A点的水平轴无摩擦转动.板的B端系有轻绳,轻绳的另一端绕过两 在光滑的水平面上有一静止物体,现以水平恒力甲推这一物体.作用一段时间后,换成相反方向的水平恒力乙推这一物体,当恒力乙作用时间与恒力甲作用时间相同时,物体恰好回到原处,此时物体 1小船匀速横渡一条河流,当船头垂直对岸航行时,在出发后的十分钟到达对岸下游一百二十米处,若船头保持与河岸成一定角度向上游航行,在出发后12.5分钟时到达正对岸,求：船在静水中的速度 -----Has Sam finished his homework today?-----I have no idea.He____ it this morning .A did B has done C was doing D had done 为什么选C啊 ..Unless_____by credit card,please pay in cash.A.pay B.is paid C.paying D.paidTo achieve his heat's desire,he is racing the clock all the time.He is not the man_____he was two years ago.A.which B.that C.who D.whomYou can't help but hear commercials,e (2008四川卷）.-You speak very good French!- Thanks.I ___ French in Sichuan University for four years.A.studiedB.studyC.was studyingD.had studied这题答案是A,为什么用过去时,而不用完成时呢? In her writing,Elimor Wylie often dealt with her own personality as it was,rather than _________ .(A) as was defines by others(B) its definitions by others(C) other's definition(D) as others defined it不要只发答案,要分析,为什么选这个? 四级英语是不是到大学都得考? 大学英语四级一定要考吗如题 1、I told him not to do it,but he just___my advice.A、ignored B、followed C、disagreed D、took2、-Have you ever been to Shanghai Expo Garden?-No.It is the first time that I ___to China.A、come B、have come C、am coming D、came3、-What abou 1 after you use the pen,you had better ____ it ____.A get in B put away C put on D take out 2 do you know the woman ______?A in the hat B wearing in red C dressing funny D having on a hat 3 I hope my suggestions are _____ helpful to you.A sooner or l 有没有关于人教版五年级下册英语的练习册给推荐一下?主要是有关句型转换、完形填空、用适当词填空等，不知道有没有专门这类的练习题， 英文的全部季节怎样拼 有一初速度为20米每秒的小球,竖直向上抛出,已知它上升的最大高度为18米,它的空气阻力恒定,求当它与地面多高时,它的动能等于重力势能,取地面为零势能面. 质量为m的物体,在距地面h高处以1/3g的加速度由门静止竖直下落到地面,物体的重力势能如何变化?动能和重力做的功的变化? 这道英语选择题应该选什么,麻烦详细分析下!辛苦了!We will graduate from middle school thid June,( ) we will be free from the pressure of study.A.then B.when答案给的是B.请问选A不可以么?为什么呢? 这道英语选择题应该选什么,辛苦了!The police men were warned the young man ( ) after drinking.A.never to drive B.to never drive C.never driving D.never drive 这道英语选择题应该选什么,辛苦了!The doctor exaimed the patient carefully,only ( ) she was not seriously ill.A.to find B.to be found这两个应该选哪个?请详细分析下, “季节”的英文怎么拼 季节的英文怎么拼 英语作文我的爸爸 某市规定,汽车在学校校门前马路上形式的速度不得超过40km/h,一次事故,某汽车在校门口的马路上留下一条长长的刹车痕.交警测量其长度为9m,又从监控资料上确定了该车从刹车到停止用时1.5s, 边长为L的正方形金属框 质量M 电阻R 悬挂在有界的 匀强磁场边缘 它的上半在磁场里 下半在外 磁场时间变化规律为B＝KT （K＞0） 细线悬挂的最大拉力是2MG 求从T0开是 多久 线被拉断 英语翻译Great change has taken place _________ 怎么填? 英语翻译：我们已经看到了在我们国家发生的巨大变化我们已经看到了在我们国家发生的巨大变化We have ____ the great ____ that have ____ ____ in our country 大学英语四级怎么考? 我要做英语ppt有没有什么好的题材..就是比较新颖的题材.额 英语作文我的父亲 1 the visiting Minister expressed his satisfaction with his talks,_ _____C_____that he had enjoyed his stay here.A having added B to add C adding D added 2.the growing speed of a plant is influenced by a number of factories,___B____are beyond our cen 2道高一的英语翻译 急!We will start at the point when we left off thereI don't know the reason why you quarreled with him SAT语法题,Some scientists believe that mentally stimulating activities may increase the number of brain cells （available to replace if any） are lost through aging.请问维护森么括号里的要改成available to replace any that,我不是 五年级下册的新世纪版英语练习册答案新世纪版 急超急!