Ⅰ.完形填空When I was about twelve years old my mother told us that we would not be __1___ Christmas gifts for lack of felt sad and thought What would I say when the other kids asked what Id __2___ Then t
Ⅰ.完形填空About five years ago I began to study at a new school when my family moved to was just a little __1__ wondering whether I could get on well with my a girl in my __2__ who I thought wasnt rea
Ⅰ.完形填空About five years ago I began to study at a new school when my family moved to was just a little __1__ wondering whether I could get on well with my a girl in my __2__ who I thought wasnt ready
Ⅰ.完形填空When I was about twelve years old my mother told us that we would not be __1___ Christmas gifts for lack of felt sad and thought What would I say when the other kids asked what Id __2___ Thenth
Ⅰ.完形填空Im an ago I traveled to the north of __1__ the heat the noisy streets the busy markets and the smell of Thai enjoyed my __2__ there very there is one thing that I wish I hadnt day I set off
一、选择题1.(多选)如图5-1-11所示,在皮带传送装置中,皮带把物体P匀速带至高处,在此过程中,下述说法正确的是( )图5-1-11A.摩擦力对物体做正功 B.摩擦力对物体做负功C.支持力对物体不做功D.合外力对物体做正功解析:选AC物体P匀速上升过程中,合力为零,合外力对物体做功为零,D错误;支持力垂直于运动方向,故支持力做功为零,C正确;摩擦力沿斜面向上,摩擦力做正功,A正确,B
一、选择题1.(单选)下列物体运动过程中满足机械能守恒的是( )A.跳伞运动员张开伞后,在空中匀速下降B.忽略空气阻力,物体竖直上抛C.火箭升空过程D.拉着物体沿光滑斜面匀速上升解析:选B跳伞运动员在空中匀速下降时,动能不变,重力势能减小,故机械能减少,A错误;忽略空气阻力,物体竖直上抛时,只有重力做功,机械能守恒,B正确;火箭升空时,推力做正功,机械能增加,C错误;拉着物体沿光滑斜面匀速上
一、选择题1.(多选)(2013·中山模拟)质量为m的物体在水平力F的作用下由静止开始在光滑地面上运动,前进一段距离之后速度大小为v,再前进一段距离使物体的速度增大为2v,则( )A.第二过程的速度增量等于第一过程的速度增量B.第二过程的动能增量是第一过程动能增量的3倍C.第二过程合外力做的功等于第一过程合外力做的功D.第二过程合外力做的功等于第一过程合外力做功的2倍解析:选AB由题意知,两
一、选择题1.(单选)一颗子弹以某一水平速度击中了静止在光滑水平面上的木块,并从中穿出,对于这一过程,下列说法正确的是( )A.子弹减少的机械能等于木块增加的机械能B.子弹减少的机械能等于系统内能的增加量C.子弹减少的机械能等于木块增加的动能和内能之和D.子弹减少的动能等于木块增加的动能与子弹和木块系统增加的内能之和解析:选D由于摩擦阻力做功,故有机械能转化为内能,子弹减少的动能转化为木块动
Ⅰ.完形填空Eye-catching crop art has sprung up across rice fields in this is not alien __1__.The designs have been cleverly planted.__2__creating the huge displays use no ink or different __3__of rice pla
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