╭──────────── 提醒：版规三及版规四 ─────────────╮ │解题文需附上自己的解题过程或自己对题目的理解 │ │问题文需先自行查过网路资料并附上对资料的初步理解 │ │问题获得回答後也勿任意删除文章，并适度的向回答者表达感谢之意 │ ╰──────────────────────────阅读後可用ctrl+y删除╯ 【出处】(习题或问题的出处) halliday 第十版 chp8 78题 【题目】(题目的文字叙述，如有图片亦可提供图片) 78 At a certain factory, 300 kg crates are dropped vertically from a packing machine onto a conveyor belt moving at 1.20 m/s (Fig. 8-62). (A motor maintains the belt’s constant speed.) The coeffi- cient of kinetic friction between the belt and each crate is 0.400. After a short time, slipping between the belt and the crate ceases, and the crate then moves along with the belt. For the period of time during which the crate is being brought to rest relative to the belt, calculate, for a coordinate system at rest in the factory, (a) the kinetic energy supplied to the crate, (b) the magnitude of the ki- netic frictional force acting on the crate, and (c) the energy sup- plied by the motor. (d) Explain why answers (a) and (c) differ. 【瓶颈】(解题瓶颈或思考脉络，请尽量详述以利回答者知道要从何处讲解指导) (错误示范：第X题我不会，求详解) (错误示范：acceleration of gravity是什麽意思我看不懂) (正确示范：我算出来的答案好像不太对，这是我的计算过程，哪里出问题?) (c)选项答案是(a)的两倍，详解说马达做的功是摩擦力做的功跟动能的增加，但是摩擦力 做的功不是转换成动能了吗？ 有点无法理解 --

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