悦作业英语周报九下2答案

第二节读后续写( One possible version)Fliss immediately took the purse to the local police station with Molly. When they arrivedFliss tied Molly to a fireplug outside and went in herself. She handed the purse to a police officerand explained everything. Greatly touched, he shook her hand and thanked her for doing her duty,promising that he would do his best to find the owner Fliss felt reassured and went back withMolly. The next day, a journalist called to make an appointment for an interview.When the journalist came, they two were on the beach. The journalist was surprised to findthat Molly was picking up litter, following her master. Fliss told the journalist it was on the wayto collecting litter that Molly had found the purse. Hearing this, Molly stopped, wagging her tailas if she understood the whole situation. Having learned about the whole story, the journalist gotto know what they did to protect the local beach. Surprised and impressed, the journalist tooksome pictures. The next day they were on the front page of the newspaper. A minor action couldmake wonders!(162 words)

11.(16分)【解答】(1)由平衡条件可知:mg=kx(2分)解得:k=mg(1分)(2)B球由静止下落后与A接触前的瞬时速度为v,则有(2分)设A与B碰撞后的速度为v,有m3v0=mg+m)v(3分磁后从粘在一起到返回O点,系统机械能守恒,取碰后瞬问所在平面为零势能面2(mB+m解得:h=3(1分)(3)当加速度为零时,两球速度达到最大值,此时弹簧压缩量为x有:(mB+m)(2分)从最大速度到返回O点,系统机械能守恒定律,取最大速度处所在平面为零势能面:m)vm +2kx (mb+m)gx(2分)解得go(1分)

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