2022高二课标英语周报第49期答案

10BC【解析】小球第一次沿轨道AC下滑的过程中,由題意可知,电场力与重力的合力方向恰好沿着斜面AC,则刚开始小球与管壁无作用力,当从静止开始运动后,由左手定则可知,洛伦兹力导致球对管壁有作用力,从而导致滑动摩擦力增大,而重力与电场力的合力√3大小为F=(mg3mk不变,故根据牛顿第二定律可知,小球做加速度减小的加速运动,当摩擦力等于两个力的合力时,做匀速运动.A错误;小球在轨道上往复运动,由于在斜轨上不断损失机械能,则最终会在CD之间往复运动,对小球在O点受力分析,且由C向D运动,此时在D点的洛伦兹力最小,对轨道的压力最小,由牛顿第二定律,则有FNg Bqv=mR,由C到O点,根据机械能守恒定律有 meRsin30°=m2,解得F=2ng-gB√gR,即当小球由C向D运动时,小球对轨道的最小弹力为2mg-qB√gR,不可能为2mg-2qB√gR·B正确;根据动能定理可知,从静止开始运动,最终运动到C点时速度为零则摩擦力做功与重力及电场力做功之和为零,则小球克服摩擦力做的总功为∽mgl,C正确;当小球的摩擦力与重力及电场力的合力相等时,小球做匀速直线运动,小球在轨道内受到的摩擦力最大,则3为-mg,不可能大于二mgD错误。故选BC

第三节One possible wersionParagraph 1I was tired. My arms were really heavy and I felt as ifthey were on fire. We were made up and down by thewaves.I didnt know how much longer I could pull that oarthrough the water. As if he heard my thinking, my fathercalled to me, "I need you, Karl. Only a little longer. "Soi kept pulling. Just when I thought I had no more strengthI heard it- the sound of waves breaking against the shoreIt refreshed us greatly and we kept pulling. At last wemoved into the shelter with all the herringParagraph 2My mother rushed through the rain to greet us."Ivebeen so worried, she said. She hugged me tightly andthen my father. Nothing to worry about, "he assured herHe put his hand on my shoulder. "You did well, son. Howdo you feel? " Tired as I was, I managed a smile."FineAnd Daddy, you ar

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