ÌâÄ¿ÄÚÈÝ
£¨18·Ö£©ÈçͼËùʾ£¬Çã½Ç
=30
µÄ×ã¹»³¤¹â»¬Ð±Ãæ¹Ì¶¨ÔÚˮƽÃæÉÏ£¬Ð±ÃæÉÏ·ÅÒ»³¤L=1.8m¡¢ÖÊÁ¿M= 3kgµÄ±¡Ä¾°å£¬Ä¾°åµÄ×îÓҶ˵þ·ÅÒ»ÖÊÁ¿m=lkgµÄСÎï¿é£¬Îï¿éÓëľ°å¼äµÄ¶¯Ä¦²ÁÒòÊý
=
£®¶Ôľ°åÊ©¼ÓÑØбÃæÏòÉϵĺãÁ¦F£¬Ê¹Ä¾°åÑØбÃæÓɾ²Ö¹¿ªÊ¼×öÔȼÓËÙÖ±ÏßÔ˶¯£®ÉèÎï¿éÓëľ°å¼ä×î´ó¾²Ä¦²ÁÁ¦µÈÓÚ»¬¶¯Ä¦²ÁÁ¦£¬È¡ÖØÁ¦¼ÓËÙ¶Èg=l0
£®
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250050269494246.png)
£¨1£©ÎªÊ¹Îï¿é²»»¬Àëľ°å£¬ÇóÁ¦FÓ¦Âú×ãµÄÌõ¼þ£»
£¨2£©ÈôF=37.5N£¬Îï¿éÄÜ·ñ»¬Àëľ°å£¿Èô²»ÄÜ£¬Çë˵Ã÷ÀíÓÉ£»ÈôÄÜ£¬Çó³öÎï¿é»¬Àëľ°åËùÓõÄʱ¼ä¼°»¬Àëľ°åºóÑØбÃæÉÏÉýµÄ×î´ó¾àÀ룮
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005026855310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005026871189.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005026886301.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005026902453.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005026933489.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250050269494246.png)
£¨1£©ÎªÊ¹Îï¿é²»»¬Àëľ°å£¬ÇóÁ¦FÓ¦Âú×ãµÄÌõ¼þ£»
£¨2£©ÈôF=37.5N£¬Îï¿éÄÜ·ñ»¬Àëľ°å£¿Èô²»ÄÜ£¬Çë˵Ã÷ÀíÓÉ£»ÈôÄÜ£¬Çó³öÎï¿é»¬Àëľ°åËùÓõÄʱ¼ä¼°»¬Àëľ°åºóÑØбÃæÉÏÉýµÄ×î´ó¾àÀ룮
£¨1£© F¡Ü30N£»£¨2£© Îï¿éÄÜ»¬Àëľ°å£¬1.2s£¬s=0.9m¡£
ÊÔÌâ·ÖÎö£º£¨1£©¶ÔM¡¢m£¬ÓÉÅ£¶ÙµÚ¶þ¶¨ÂÉF££¨M+m£©gsin¦Á=£¨M+m£©a £¨2·Ö£©
¶Ôm£¬ÓÐf£mgsin¦Á=ma £¨2·Ö£©
F¡Ümgcos¦Á £¨2·Ö£©
´úÈëÊý¾ÝµÃ£ºF¡Ü30N £¨1·Ö£©
£¨2£©F=37.5N>30N£¬Îï¿éÄÜ»¬Àëľ°å £¨1·Ö£©
¶ÔÓÚM£¬ÓÐF£¦Ìmgcos¦Á£Mgsin¦Á=Ma1 £¨1·Ö£©
¶Ôm£¬ÓЦÌmgcos¦Á£mgsin¦Á=ma2 £¨1·Ö£©
ÉèÎï¿é»¬Àëľ°åËùÓõÄʱ¼äΪt£¬ÓÉÔ˶¯Ñ§¹«Ê½£º
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005026980338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005026980338.png)
´úÈëÊý¾ÝµÃ£ºt=1.2s£¨1·Ö£©
Îï¿éÀ뿪ľ°åʱµÄËÙ¶Èv=a2t£¨2·Ö£©
Óɹ«Ê½£º£2gsin¦Ás=0£v2£¨2·Ö£©
´úÈëÊý¾ÝµÃs=0.9m¡££¨1·Ö£©
![](http://thumb2018.1010pic.com/images/loading.gif)
Á·Ï°²áϵÁдð°¸
Ïà¹ØÌâÄ¿