Question

15£®Ð¡Ã÷ÀûÓÃÊî¼Ùȥѧϰ¼ÝÊ»¼¼Êõ£¬ÆäÖÐÄ¿±êÍ£³µÊÇÒ»¸ö±Ø¿¼ÌâÄ¿£¬ÆäÔ˶¯¹ý³Ì¿É¼ò»¯ÎªÈçͼËùʾµÄÄ£ÐÍ£ºÔÚƽֱ¹«Â·ÉÏÓÐA¡¢B¡¢CÈý¸öÍ£³µ±êÖ¾¸Ë£¬ÏàÁÚ±êÖ¾¸Ë¼ä¾àÀë¡÷x=20m£®Ä³´Î²âÊÔʱ£¬Ð¡Ã÷ÕýÒÔv₀=20m/sµÄËÙ¶ÈÔÈËÙÐÐÊ»£¬µ±³µÍ·µ½´ïOµãʱÌýµ½Í£³µÖ¸ÁСÃ÷¾­¹ý¡÷t=0.5sµÄ·´Ó¦Ê±¼äºó¿ªÊ¼É²³µ£¬É²³µºó¿ªÊ¼×öÔȼõËÙÖ±ÏßÔ˶¯£¬Èô²âµÃÆû³µ´ÓOµ½±êÖ¾¸ËAµÄʱ¼äΪt₁=4.5s£¬´Ó±êÖ¾¸ËAµ½±êÖ¾¸ËBµÄʱ¼äΪt₂=2.0s£®Çó£º

£¨1£©Oµãµ½±êÖ¾¸ËAÖ®¼äµÄ¾àÀëx£»
£¨2£©Æû³µÍ£Ö¹Ô˶¯Ê±³µÍ·Óë±êÖ¾¸ËCµÄ¾àÀëL£®

Answer 1

·ÖÎö £¨1£©¸ù¾Ýij¶Îʱ¼äÄÚµÄƽ¾ùËٶȵÈÓÚÖмäʱ¿ÌµÄ˲ʱËÙ¶ÈÇó³öABÖмäʱ¿ÌµÄʱ¿ÌµÄ˲ʱËٶȣ¬½áºÏËÙ¶Èʱ¼ä¹«Ê½Çó³öÆû³µÉ²³µÊ±µÄ¼ÓËٶȴóС£¬¸ù¾ÝλÒÆʱ¼ä¹«Ê½Çó³öOAµÄ¾àÀ룬´Ó¶øµÃ³öOAµÄ¾àÀ룮
£¨2£©¸ù¾ÝËÙ¶Èʱ¼ä¹«Ê½Çó³öBµãµÄËٶȣ¬½áºÏËÙ¶ÈλÒƹ«Ê½Çó³ö´ÓBµãµ½Í£Ö¹µÄ¾àÀ룬´Ó¶øµÃ³öÆû³µÍ£Ö¹Ô˶¯Ê±³µÍ·Óë±êÖ¾¸ËCµÄ¾àÀëL£®

½â´ð ½â£º£¨1£©Æû³µÍ¨¹ýABÖмäʱ¿ÌµÄ˲ʱËÙ¶ÈΪ£º${v}_{1}^{\;}=\frac{¡÷x}{{t}_{2}^{\;}}=10m/s$
Æû³µ´Óɲ³µµ½ABÖмäʱ¿ÌµÄʱ¼äΪ£ºt=4.5+1-0.5s=5s£¬
Ôòɲ³µÊ±µÄ¼ÓËٶȴóСΪ£º$a=\frac{{v}_{0}^{\;}-{v}_{1}^{\;}}{t}=2m/{s}_{\;}^{2}$
´ÓOµãµ½AµãµÄ¾àÀëΪ£º${x}_{OA}^{\;}={v}_{0}^{\;}¡÷t+{v}_{0}^{\;}£¨{t}_{1}^{\;}-¡÷t£©-\frac{1}{2}a£¨{t}_{1}^{\;}-¡÷t£©_{\;}^{2}$=74m
£¨2£©BµãµÄËٶȣº${v}_{B}^{\;}={v}_{1}^{\;}-a\frac{{t}_{2}^{\;}}{2}=8m/s$
Ôò´ÓBµãµ½Í£Ö¹µÄ¾àÀ룺$x¡ä=\frac{{v}_{B}^{2}}{2a}=16m$
ËùÒÔÆû³µÍ£Ö¹Ô˶¯Ê±³µÍ·Óë±êÖ¾¸ËCµÄ¾àÀëΪ£ºL=¡÷x-x¡ä=20 m-16m=4m£®
´ð£º£¨1£©Oµãµ½±êÖ¾¸ËAÖ®¼äµÄ¾àÀëxΪ74m£»
£¨2£©Æû³µÍ£Ö¹Ô˶¯Ê±³µÍ·Óë±êÖ¾¸ËCµÄ¾àÀëLΪ4m£®

µãÆÀ ´ËÌâÒªÀí½â·´Ó¦Ê±¼äÄÚÆû³µ¼ÌÐø×öÔÈËÙÔ˶¯£¬»¹ÒªÑø³É»­Ô˶¯¹ý³ÌʾÒâͼ£¬ÕÒλÒÆÖ®¼äµÄ¹Øϵ£®´ËÌâÓÐÒ»¶¨µÄÄѶȣ¬ÊôÓÚÖеµÌ⣮