英语周报高二课标提升版20期答案

可得mv=十m防2分)解得碰后小球的速度幼=1m/s(1分)在碰撞中对系统由能量守恒定律得损失的机檢能△E=号m一号m可一量m通一1(2分)15.【解析】(1)根据动能定可知m1gl(1-cs0)=(1分所以碰前瞬间小球的速度v=2m/s(1分)(2)根据动能定理可知碰后物块的速度满足- gs=0-m2v2(1分)则碰后物块的速度v2=2m/s(1分)小球和物块组成的系统水平方向动量守恒,以向右为正方向

第二节Dear WangmingHow are you recently? I am sorry that I haven't written to you so long, ow my familycoronavirus hasntare very up. You must knowthe novbeen controlled effectivelysince it broke out in the US and so many people are being infected every day. So we dare notgo out because ofYou are lucky. When the novel coronavirus broke out in China, thegovernment took strong and effective measures and controlled its spread. There have been nolocal cases of infected people since September. China is great! Chinese people are lucky! Ireally regret coming here sometimes. I hope that I can return to our motherland as soon aspossibleFinally may you make great progress!LiHua.

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