2020至2022英语周报人教版第33期答案

第二节书面表达Dear LiOn behalf of the Students'Union of our school, I'm writing to express ourheartfelt thanks for your wonderful speech on AIWe Chinese have a saying that listening to your words for an hour is morebeneficial than reading for ten years. We have learned a lot from your speechindeed. Having heard your speech, we not only gain a better understanding ofwhat AI is, but we're also aware of what effects it might have on us humanbeings. We do hope you'll come to our school to deliver more brilliant speechesin the near futureThanks again!Yours sincerelyLi Hu

21.BC解析:本题考査传送带问题。由υt图像得0~1s煤块的加速度大小a1=8m/s,方向沿传送带向下;1s~2s内,煤块的加速度大小a3-4m/s2,方向沿传送带向下;0~1s内,对煤块应用牛顿第二定律得nisinθ anglosθ-ma1;1s~2s,对煤块应用牛顿第二定律得 nisin0- anglosθ=mn2;解得θ=37°,0.25,Δ项错误、B项正确。σ-t图线与t坐标轴所围面积表示位移,所以煤块上滑的总位移x=10m,由运动学公式得下滑时间下=√/2x=5,所以煤块从冲上传送带到返回A端所用的时间为(2 5),C项正确。0~1s内煤块比传送带多运动4m,划痕长4m;1s~2s内传送带比煤块多运动2m,产生的热量为12J,D项错误。

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