题目内容
在“验证平行四边形定则”的实验中,用A、B两个弹簧秤拉橡皮条的结点,使其位于O处,如图所示,此时,
,现在保持A读数不变,减小
角,要使结点仍在O处,可采用的办法是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250010362916673.png)
A.增大B的读数,同时减小
角
B.减小B的读数,同时减小
角
C.增大B的读数,同时增大
角
D.保持B的读数不变,同时增大
角
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001036120618.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001036245312.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250010362916673.png)
A.增大B的读数,同时减小
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001036307338.png)
B.减小B的读数,同时减小
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001036307338.png)
C.增大B的读数,同时增大
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001036307338.png)
D.保持B的读数不变,同时增大
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001036307338.png)
B
试题分析:要保证结点不动,应保证合力不变,则由平行四边形定则作图如下:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250010363697825.png)
由图可知:合力不变,A方向向合力方向靠拢即减小α角,则B的拉力应减小,同时应减小β角;故ACD错误,B正确.
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目