2022-2022 英语周报 七年级新目标(GDY)第25期答案

5.CD【解析】设物块A的质量为m,对A、B整体受力分析如图所示,可知斜面对B有支持力和沿斜面向上的摩擦力,故斜面与B之间仅存在2对作用力与反作用力,A错误;将细线对C的拉力沿着杆的方向和垂直杆的方向分解, Frcos=mg,解得FT=0.5mg,将A、B视为整体,斜面对B的作用力为支持力FN和摩擦力F的合力,整体受力平衡,此合力与整体重力3ng,细线的拉力05m的合力等大反向,故斜面对B的作用为方向指向左上方,大小为F=amg)+(0.m//37N,B错误;细线剪断之后假B一起运动,则根据牛顿第二定律有3 ng sIn37”-p×3 Ig cos37=3ma,解得a=2m/s2,B之间的静摩擦力足以提供其加速度,故假设成立A、B未发生相对滑动,A沿水平方向的加速度由静摩擦力提供,可知Fa=mcos37=0.16N,C正确;A沿竖直方向的加速度由重力和所受支持力的合力提供,有mg-FNA= mia sin37°,解得FN=0.88N,D正确

短文改错A professor gave a balloon to every student, whom had to write their name on it or throw it in thewhoandhallway. The professor then mixed all the balloon, The students were given 5 minutes to find their ownballoonsballoon.Despite of a busy search, no one found their balloon. At that point the professor told the students totaking the first balloon that they found and hand it to A person whose name was written on it. SurprisingtaketheSurprisinglyeveryone had their own balloon soon. Thehe professor said to the students: "These balloons is like happiness.areWe would never find it if everyone is looking for their own. But if we care about other people,'s happinessllwe'll find our too."ours

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