题目内容
利用单摆验证小球平抛运动规律,设计方案如图甲所示,在悬点O正下方有水平放置的炽热的电热丝P,当悬线摆至电热丝处时能轻易被烧断;MN为水平木板,已知悬线长为L,悬点到木板的距离
.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082422041070011114.jpg)
(1)电热丝P必须置于悬点正下方的理由是:__________________________________
________________________________________________________________________.
(2)将小球向左拉起后自由释放,最后小球落到木板上的C点,
,则小球做平抛运动的初速度
为________.
(3)在其他条件不变的情况下,若改变释放小球时悬线与竖直方向的夹角θ,小球落点与O′点的水平距离x将随之改变,经多次实验,以
为纵坐标、
为横坐标,得到如图乙所示图象.则当
时,x为________ m;若悬线长
,悬点到木板间的距离
为________ m.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220409265732.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082422041070011114.jpg)
(1)电热丝P必须置于悬点正下方的理由是:__________________________________
________________________________________________________________________.
(2)将小球向左拉起后自由释放,最后小球落到木板上的C点,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220411496490.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220412416323.png)
(3)在其他条件不变的情况下,若改变释放小球时悬线与竖直方向的夹角θ,小球落点与O′点的水平距离x将随之改变,经多次实验,以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220413477338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220414803426.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220415567476.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220416425457.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220417221366.png)
(1)以保证小球做平抛运动. (2)
(3)0.52 1.5
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220417970781.png)
试题分析:(1)电热丝P放在悬点正下方,是因为当小球摆到最低点时,悬线刚好被烧断,以保证小球做平抛运动.
(2)由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220419421477.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220420310711.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220421620929.png)
(3)由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220422728558.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220423617658.png)
当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220415567476.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220425629583.png)
当
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220426035500.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220426799526.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220427517531.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220428749490.png)
小球在最低点的速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220429826976.png)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242204303411062.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220431043509.png)
点评:本题难度中等,在解(3)时一定要充分利用
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220422728558.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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