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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颜很秦5110怎么判断机械能守恒? -
扶弦丽15056002055 ______ 只有重力做功,即1 物体只受重力,不受其他的力,如自由落体运动和各种抛体运动2 除重力外还受其他的力,但其他力不做功,如物体沿光滑斜面的运动3 只与初末位置有关,与物体所走的路径无关4 动能和势能相互转化5 也可是系统的机械能守恒
颜很秦5110如何判断物体是否机械能,动能等守恒 -
扶弦丽15056002055 ______ 系统内只有弹力或重力做功或只有二者同时做功时机械能守恒. 根据Ek=mv²/2可得,对于同一物体,在保证机械能守恒的条件下,v不变即做匀速直线运动时动能守恒 希望对你有所帮助~~有不懂的可以百度hi'我~~~
颜很秦5110怎么判断机械能是否守恒
扶弦丽15056002055 ______ 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.
颜很秦5110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? -
扶弦丽15056002055 ______[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...
颜很秦5110怎样判断一个系统内机械能是否守恒 -
扶弦丽15056002055 ______ 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.
颜很秦5110如何判断系统内机械能守横?
扶弦丽15056002055 ______ 可以用两种方法 1.只有重力做功,其他力都不做功的情况下机械能守恒 2.因为机械能是动能和重力势能的总和,所以看动能和重力势能有没有变化; 如果没有变化,或者增大量和减小量相等时,机械能守恒
颜很秦5110如何判别机械能是否守恒
扶弦丽15056002055 ______ 很简单,看机械能有没有转化为其他形式的能量 如有没有发热转化为内能,有没有发光转化为光能,有没有产生电流,转化为电能等 …… 有阻力,机械能就不守恒,会转化为内能(摩擦生热) 当然是电梯做的总功增加机械能,因为受外力作用电梯要经过一定位移,做功增加了机械能,同时重力做功增加了势能
颜很秦5110判断机械能是否守恒的方法 -
扶弦丽15056002055 ______ 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
颜很秦5110如何知道系统机械能是否守恒 -
扶弦丽15056002055 ______ 你得看看除了重力和系统内力以外有没有其它力做功还得看看有没有热产生
颜很秦5110如何判别机械能守恒? -
扶弦丽15056002055 ______ 1当然能,上抛物体时机械能守恒,但重力是阻力,阻碍物体向上运动;2是电梯给的力使机械能不守恒
