专题06 机械能守恒定律 能量守恒定律

目 录

01机械能转化及守恒的判断 2

考向一：机械能转化及守恒的判断 2

02 机械能守恒定律的应用 7

考向一：机械能的图像类问题 7

考向二：单个物体的机械能守恒 15

考向三：多个物体(系统)的机械能守恒 18

03能量转化及守恒定律的综合应用 20

考向一：能量转化及守恒定律的综合应用 20

考向四：涉及弹簧的能量问题 22

考向二：涉及板块、传送带的能量问题 33

01机械能转化及守恒的判断

考向一：机械能转化及守恒的判断

1．（2023·浙江·高考真题）一位游客正在体验蹦极，绑上蹦极专用的橡皮绳后从跳台纵身而下。游客从跳台下落直到最低点过程中（ ）

A．弹性势能减小 B．重力势能减小

C．机械能保持不变 D．绳一绷紧动能就开始减小

3．（2022·浙江·高考真题）神舟十三号飞船采用“快速返回技术”，在近地轨道上，返回舱脱离天和核心舱，在圆轨道环绕并择机返回地面。则（ ）

A．天和核心舱所处的圆轨道距地面高度越高，环绕速度越大

B．返回舱中的宇航员处于失重状态，不受地球的引力

C．质量不同的返回舱与天和核心舱可以在同一轨道运行

D．返回舱穿越大气层返回地面过程中，机械能守恒

5．（2021·浙江·高考真题）如图所示，同学们坐在相同的轮胎上，从倾角相同的平直雪道先后由同高度静止滑下，各轮胎与雪道间的动摩擦因数均相同，不计空气阻力。雪道上的同学们（ ）

A．沿雪道做匀速直线运动 B．下滑过程中机械能均守恒

C．前后间的距离随时间不断增大 D．所受重力沿雪道向下的分力相同

7．（2024·广东江门·统考模拟预测）蹦极是一项非常刺激的体育项目，而“反向蹦极”是一项比蹦极更加刺激的运动。如图所示，弹性轻绳上端固定在P点，下端固定在玩家的身上并向下拉长与固定在地面上的安全扣环相连。打开安全扣环后，玩家从c点开始由静止释放，像“火箭发射一般竖直向上运动”，上升到b点时速度最大，轻绳在a点为原长位置，玩家到达的最高点在P与a之间，不计空气阻力，下列说法正确的是（ ）

A．人在c到a运动过程中都做加速运动

B．人在c到b运动过程中做加速度减小的加速运动

C．在整个运动过程中，玩家的机械能守恒

D．人在b到最高点的运动过程中，玩家处于超重状态

8．（2024·广东惠州·统考二模）2023年10月3日，在杭州亚运会蹦床项目女子决赛中，中国选手朱雪莹夺冠，图为朱雪莹在东京奥运会上决赛时腾空后下落的照片，朱雪莹从刚接触床面到运动至最低点的过程中，下列说法正确的是（ ）

A．朱雪莹刚接触床面时速度最大

B．朱雪莹在该过程中始终处于失重状态

C．在该过程中朱雪莹的动能减少量等于弹性势能的增加量

D．在该过程中蹦床对朱雪莹一直做负功

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嵇娥伊2250如何判断系统机械能守恒?我知道怎么判断一件物体的机械能是否守恒,但我不知道怎么判断系统机械能是否守恒?是能量互相转化时就守恒吗? -
蓟荆治15231243408 ______[答案] (1)做功条件分析法:机械能守恒 当发生动能与重力势能的转化时,只有重力做功,当发生动能与弹性势能的转化时,只有弹力做功,其他力均不做功,则系统的机械能守恒. (2)能量转换分析法: 若只有系统内物体间动能和重力势能及弹性势能的...

嵇娥伊2250如何正确判断“机械能是否守恒和物体系是否遵循动量守恒定律. -
蓟荆治15231243408 ______[答案] 机械能是否守恒 判断是有无除重力之外的力做功 (即有无机械能有无向其他能转化) 动量守恒定律 一个系统不受外力或所受外力之和为零 或者瞬间的内力大大于外力,比如爆炸

嵇娥伊2250怎么判断动量守恒和机械能守恒? -
蓟荆治15231243408 ______[答案] 动量是否守恒的关键在于系统受到外力作用.如果系统不受外力或者所受合外力为0,则系统动量守恒,反之则不守恒.(但是如果系统在某个方向上受合外力为0,则可以说系统在这个方向上动量守恒,注意,是“在这个方向上”守恒) 而机械能是否...

嵇娥伊2250怎么判断机械能是否守恒
蓟荆治15231243408 ______ 第一看是否只有重力做功,如果是则守恒.第二其它力也做功不过它们只和为零,也就是有一个正功或者多个正功,有一负功或多个负功,不管多少其它力(不包括重力)做功为零的,机械能守恒.

嵇娥伊2250有时候常常遇到机械能不变的情况被作为机械能守恒判断, -
蓟荆治15231243408 ______[答案] 判断一物体是否机械能守恒.只需要看它受力的做工情况.如果它只有重力或弹力做功,则机械能守恒.这里也要注意一点,看是物体有哪些力做功,而不是看物体受哪些力.如果物体除受重力或弹力之外的外力,但是外力并不做功,那...

嵇娥伊2250如图所示,下列关于机械能是否守恒的判断正确的是( ) -
蓟荆治15231243408 ______[选项] A. 甲图中,火箭升空的过程中,若匀速升空机械能守恒,若加速升空机械能不守恒 B. 乙图中物体匀速运动,机械能守恒 C. 丙图中小球做匀速圆周运动,机械能守恒 D. 丁图中,轻弹簧将A、B两小车弹开,两小车组成的系统机械能不守恒,两小车和弹簧组成的系统机械能守恒

嵇娥伊2250怎么快捷的判断机械能是否守恒 -
蓟荆治15231243408 ______ 当只有重力或系统内弹力对物体做功,其它力对物体不做功时,物体的机械能守恒. 判断机械能守恒时,一看物体有没有受到除重力或系统内弹力以外的力﹙如:拉力 ,推力,摩擦力……﹚,二看该力有没有对物体做功,若做了功,且做正功,则该物体机械能增大,若做负功,则机械能减小.

嵇娥伊2250如何引导初中学生理解机械能守恒的条件 -
蓟荆治15231243408 ______[答案] 简介 物理知识点:如何理解机械能守恒条件的本质 “用细绳拴着一个小球,使小球在光滑的水平面上做匀速圆周运动.”判断此过程中小球的机械能是否守恒. 机械能守恒定律的表述为:在一过程中若外力不做功,又每一对内非保守力不做功...

嵇娥伊2250判断机械能是否守恒的方法 -
蓟荆治15231243408 ______ 只有势能(如重力、弹性、电)和动能之间相互转化而没有其他形式能掺和的时候,机械能守恒

嵇娥伊2250怎样判断一个系统内机械能是否守恒 -
蓟荆治15231243408 ______ 一个系统只有重力,或系统内的弹力做功时系统的机械能守恒.判断物体的机械能守恒是看是否有除重力和系统内的弹力以外的力做功,若外力使物体沿力的方向发生位移,则外力对物体做正功,则机械能增加,否则反之.