卷行天下的答案如何获得

卷行天下的答案如何获得 ，目前我们已经整理了卷行天下的答案如何获得 的各科答案和试卷，更多试卷答案请关注本答案网。

短文改错：Hello,everyone!It is my honor to deliver a speech on keeping air clean.As is know to us,we humansknowncan't live without air,just as fish can't live without water.However,the World Health Organization has re-cently announced a shocked study about the air we breathe.It has found that almost everyone on the earthshockingbreathe unhealthy air.The data is rough from 600 cities in 117 countries.The study shows that mostly of thebreathesroughlymostworld's people breathe the air that it breaks WHO air quality limits.As a result,million of people die everymillionsyear because A pollution-related diseases.Therefore,it was important for us to take action to solve theof1Senvironment problems and keep the air clean.environmental

21.AC【解析】小球从A点做平地运动到B点，则有R=,R=之g,解得队=√，若小球对上、下管壁均无压力，则mg=震，解得=Rg,因为<√Rg,所以管壁对小球有向上的支持力，则mgN=袋，解得N,=之mg,由牛顿第三定律可知小球对管壁的压力N,=号m之mg,A项正确，B项错误；小球到B点时竖直方向的速度)y=√2gR,在B点与管壁碰撞，水平速度减为零，从B点到P点的过3程由机械能守恒定律得2mG十mgR=亨m听，在P点对小球由牛顿第二定律得N2一mg=尽，解得N2=5mg,由牛顿第三定律可知小球对管壁的压力Np=5g,C项正确，D项错误。