ÌâÄ¿ÄÚÈÝ
ÈçͼËùʾ£¬ÖÊÁ¿·Ö²¼¾ùÔȵij¤·½ÐÎľ°åABµÄ³¤¶ÈL=4m£¬ÖÐÑëÖ§ÓÚÖ§¼ÜOÉÏ£¬A¡¢B¶Ë·Ö±ðÓÃϸÉþAD¡¢BCϵÓÚÌ컨°åÉÏ£¬Ä¾°åABˮƽʱ£¬ÉþAD¡¢BC¸ÕºÃ±ÁÖ±£¬ÇÒADÉþÊúÖ±£¬BCÉþÓë°åAB³É30¡ã½Ç£¬ÒÑ֪ϸÉþ³ÐÊܵÄ×î´óÀÁ¦¾ùΪ360N£®ÏÖÓÐÖØΪ300NµÄСº¢£¬´ÓOµã³ö·¢£®£¨1£©Èç¹ûÑØOA·½ÏòÏòA¶Ë»ºÂýÐÐ×ߣ®µ±Ð¡º¢ÐÐ×ßµ½¾àÀëOµã1.5mµÄEµãʱ£®ADÉþÉϵÄÀÁ¦ÊǶà´ó£¿
£¨2£©Èç¹ûÑØOB·½ÏòÏòB¶Ë»ºÂýÐÐ×ߣ¬ÔÚ±£Ö¤Ï¸Éþ²»±»À¶ÏµÄÇé¿öÏ£¬Ð¡º¢ÏòÓÒÐÐ×ßµÄ×î´ó¾àÀëÊǶàÉÙm£¿
·ÖÎö£º£¨1£©Ð¡º¢²úÉúµÄÁ¦¾ØÓëDAµÄÁ¦¾Øƽºâ£¬ÓÉƽºâ¹Øϵ¿ÉµÃADÀÁ¦£»
£¨2£©ÏòB¶Ë×ßʱ£¬Ð¡º¢µÄÁ¦¾ØÓëCBµÄÁ¦¾Øƽºâ£¬×÷³öÁ¦±Û£¬ÓÉÁ¦¾Øƽºâ¿ÉÇó£®
£¨2£©ÏòB¶Ë×ßʱ£¬Ð¡º¢µÄÁ¦¾ØÓëCBµÄÁ¦¾Øƽºâ£¬×÷³öÁ¦±Û£¬ÓÉÁ¦¾Øƽºâ¿ÉÇó£®
½â´ð£º½â£º£¨1£©µ±Ð¡º¢ÔÚOA²àʱ£¬CBËɳۣ¬ÈËÓëDAµÄÁ¦¾Øƽºâ£¬ÓÉƽºâ·½³ÌÖª£º
G1?0E=F?OA
´úÈëÊý¾ÝµÃ£º300N¡Á1.5m=F?2m
F=225N£®
£¨2£©Ð¡º¢ÔÚB²àʱ£¬B²úÉúÀÁ¦£¬BÀÁ¦µÄ¾ØÓëÈ˵ÄÁ¦¾Øƽºâ£¬ÀÁ¦µÄÁ¦±ÛΪ£º
sin¦È
ÉèÈË×ßµÄ×îÔ¶¾àÀëΪL£¬ÓÉÁ¦¾ØƽºâµÃ£º
G1?L=Fmax?
sin¦È
L=
=1.2m
½â£º£¨1£©ADÉþÉϵÄÀÁ¦Îª225N£¬£¨2£©ÈËÏòÓÒÐÐ×ßµÄ×î´ó¾àÀëΪ1.2m£®
G1?0E=F?OA
´úÈëÊý¾ÝµÃ£º300N¡Á1.5m=F?2m
F=225N£®
£¨2£©Ð¡º¢ÔÚB²àʱ£¬B²úÉúÀÁ¦£¬BÀÁ¦µÄ¾ØÓëÈ˵ÄÁ¦¾Øƽºâ£¬ÀÁ¦µÄÁ¦±ÛΪ£º
L |
2 |
ÉèÈË×ßµÄ×îÔ¶¾àÀëΪL£¬ÓÉÁ¦¾ØƽºâµÃ£º
G1?L=Fmax?
L |
2 |
L=
360N¡Á1m |
300N |
½â£º£¨1£©ADÉþÉϵÄÀÁ¦Îª225N£¬£¨2£©ÈËÏòÓÒÐÐ×ßµÄ×î´ó¾àÀëΪ1.2m£®
µãÆÀ£º±¾ÌâΪÁ¦¾ØƽºâµÄÁÙ½çÎÊÌ⣬Ӧ¿¼Âǵ½µ±Ð¡º¢×ßµ½×îÔ¶µãʱ£¬Éþ×ÓµÄÀÁ¦Ç¡ºÃΪ360N£®
Á·Ï°²áϵÁдð°¸
Ïà¹ØÌâÄ¿