题目内容
重庆一中物理实验小组进行“验证牛顿第二定律”的实验,图甲为实验装置简图。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082417242656817432.png)
(1)图乙所示为某小组在实验中通过打点计时器得到的一条清晰纸带,纸带上两相邻计数点的时间间隔为T=0.10s,若测得
,则打D点时小车的瞬时速度
= m/s,小车加速度a= m/s2。(以上计算结果均保留二位有效数字)
如果实验时电网中交变电流的实际频率
偏大,而做实验的同学并不知道,那么加速度的测量值比实际值 。(填“偏大”或“偏小”)。
(2)某组同学实验后得到了如图丙所示的两条a-F 图线。
(Ⅰ)图线①不过原点的原因是: ;
(Ⅱ)图线②不过原点的原因是: ;
(Ⅲ)分析丙图可得小车质量m= kg;假设得到图线②时长木板水平且小车和木板间的摩擦为滑动摩擦,则他们接触面间的动摩擦因数μ= 。(g取10m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082417242656817432.png)
(1)图乙所示为某小组在实验中通过打点计时器得到的一条清晰纸带,纸带上两相邻计数点的时间间隔为T=0.10s,若测得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172426787986.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172427021345.png)
如果实验时电网中交变电流的实际频率
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172427301318.png)
(2)某组同学实验后得到了如图丙所示的两条a-F 图线。
(Ⅰ)图线①不过原点的原因是: ;
(Ⅱ)图线②不过原点的原因是: ;
(Ⅲ)分析丙图可得小车质量m= kg;假设得到图线②时长木板水平且小车和木板间的摩擦为滑动摩擦,则他们接触面间的动摩擦因数μ= 。(g取10m/s2)
(1)
,
,偏小。
(2)(Ⅰ)平衡摩擦时倾角过大;
(Ⅱ)未平衡摩擦力或平衡摩擦力时倾角偏小;
(Ⅲ)0.5kg;0.2。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172427613584.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172427863642.png)
(2)(Ⅰ)平衡摩擦时倾角过大;
(Ⅱ)未平衡摩擦力或平衡摩擦力时倾角偏小;
(Ⅲ)0.5kg;0.2。
试题分析:(1)根据匀变速直线运动中点时刻的速度等于平均速度,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172428144897.png)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172428503572.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241724287371312.png)
如果实验时电网中交变电流的实际频率
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172427301318.png)
(2)(Ⅰ)由实验注意事项和题意可知图线①不过原点的原因是:平衡摩擦时倾角过大;
(Ⅱ)由实验注意事项和题意可知图线②不过原点的原因是:未平衡摩擦力或平衡摩擦力时倾角偏小;
(Ⅲ)由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172429267634.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172429470746.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172429751382.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172430000711.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172430297541.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172430499645.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172430749475.png)
点评:此类问题计算某一点的瞬时速度用平均速度等于中点时刻的速度,加速度用
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172428503572.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172429751382.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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