题目内容
(20分)
如图,ABD为竖直平面内的光滑绝缘轨道,其中AB段是水平的,BD段为半径R=0.2m的半圆,两段轨道相切于B点,整个轨道处在竖直向下的匀强电场中,场强大小E=5.0×103V/m。一不带电的绝缘小球甲,以速度υ0沿水平轨道向右运动,与静止在B点带正电的小球乙发生弹性碰撞。已知甲、乙两球的质量均为m=1.0×10-2kg,乙所带电荷量q=2.0×10-5C
,g取10m/s2。(水平轨道足够长,甲、乙两球可视为质点,整个运动过程无电荷转移)
(1) 甲乙两球碰撞后,乙恰能通过轨道的最高点D,求乙在轨道上的首次落点到B点的距离;
(2)在满足(1)的条件下。求的甲的速度υ0;
(3)若甲仍以速度υ0向右运动,增大甲的质量,保持乙的质量不变,求乙在轨道上的首次落点到B点的距离范围。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412163571518577.gif)
如图,ABD为竖直平面内的光滑绝缘轨道,其中AB段是水平的,BD段为半径R=0.2m的半圆,两段轨道相切于B点,整个轨道处在竖直向下的匀强电场中,场强大小E=5.0×103V/m。一不带电的绝缘小球甲,以速度υ0沿水平轨道向右运动,与静止在B点带正电的小球乙发生弹性碰撞。已知甲、乙两球的质量均为m=1.0×10-2kg,乙所带电荷量q=2.0×10-5C
,g取10m/s2。(水平轨道足够长,甲、乙两球可视为质点,整个运动过程无电荷转移)
(1) 甲乙两球碰撞后,乙恰能通过轨道的最高点D,求乙在轨道上的首次落点到B点的距离;
(2)在满足(1)的条件下。求的甲的速度υ0;
(3)若甲仍以速度υ0向右运动,增大甲的质量,保持乙的质量不变,求乙在轨道上的首次落点到B点的距离范围。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412163571518577.gif)
(20分)
解:(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635793563.gif)
解:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635730412.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635777974.gif)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635793563.gif)
(20分)
解:(1)在乙恰能通过轨道最高点的情况下,设乙到达最高点速度为
,乙离开
点到达水平轨道的时间为
,乙的落点到
点的距离为
,则
①
②
③
联立①②③得
④
(2)设碰撞后甲、乙的速度分别为
、
,根据动量守恒定律和机械能守恒定律有
⑤
⑥
联立⑤⑥得
⑦
由动能定理,得
⑧
联立①⑦⑧得
⑨
(3)设甲的质量为
,碰撞后甲、乙的速度分别为
,根据动量守恒定律和机械能守恒定律有
⑩
11
联立⑩11得
12
由12和
,可得
13
设乙球过D点时速度为
,由动能定理得
14
联立91314得
15
设乙在水平轨道上的落点距
点的距离
,有
16
联立②1516得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635793563.gif)
解:(1)在乙恰能通过轨道最高点的情况下,设乙到达最高点速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635808213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635824210.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635839185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635855206.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635871187.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635886622.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635902738.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635917374.gif)
联立①②③得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635730412.gif)
(2)设碰撞后甲、乙的速度分别为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635949207.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635949205.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635964547.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635980762.gif)
联立⑤⑥得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635995247.gif)
由动能定理,得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636027919.gif)
联立①⑦⑧得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635777974.gif)
(3)设甲的质量为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636042327.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636073375.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636354604.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636432838.gif)
联立⑩11得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636448593.gif)
由12和
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636619417.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636822464.gif)
设乙球过D点时速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636838219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636853928.gif)
联立91314得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636869602.gif)
设乙在水平轨道上的落点距
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635855206.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636900193.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121636916383.gif)
联立②1516得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121635793563.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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