Question

2£®ÈçͼËùʾ£¬t=0ʱ£¬ÖÊÁ¿Îª0.2kgÎïÌå´Ó¹â»¬Ð±ÃæÉϵÄAµãÓɾ²Ö¹¿ªÊ¼×öÔȼÓËÙÖ±ÏßÔ˶¯£¬¾­¹ýBµãºó½øÈëˮƽÃæ×öÔȼõËÙÖ±ÏßÔ˶¯£¨Éè¾­¹ýBµãÇ°ºóËٶȴóС²»±ä£©£¬×îºóÍ£ÔÚCµã£®²âµÃÿ¸ô2sµÄÈý¸öʱ¿ÌÎïÌåµÄ˲ʱËٶȼǼÔÚϱíÖУ¬ÓÉ´Ë¿ÉÖª£¨¡¡¡¡£©

t/s	0	2	4	6
v/£¨m•s-1£©	0	8	12	8

• A£® ÎïÌåÔ˶¯¹ý³ÌÖеÄ×î´óËÙ¶ÈΪ12m/s
• B£® t=$\frac{10}{3}$sµÄʱ¿ÌÎïÌåÇ¡ºÃ¾­¹ýBµã
• C£® t=10sµÄʱ¿ÌÎïÌåÇ¡ºÃÍ£ÔÚCµã
• D£® A¡¢B¼äµÄ¾àÀëСÓÚB¡¢C¼äµÄ¾àÀë

Answer 1

·ÖÎö ¸ù¾Ý±í¸ñÖеÄÊý¾ÝÇó³öÔȼÓËÙºÍÔȼõËÙÖ±ÏßÔ˶¯µÄ¼ÓËٶȣ¬½áºÏËÙ¶Èʱ¼ä¹«Ê½£¬¸ù¾Ý4sÄ©µÄËÙ¶ÈÇó³öÎïÌå2sºóÔÙбÃæÉÏ»¹Ð軬ÐеÄʱ¼ä£¬´Ó¶øµÃ³öAB¶ÎµÄʱ¼ä£¬¸ù¾ÝËÙ¶Èʱ¼ä¹«Ê½Çó³ö×î´óËٶȣ®¸ù¾Ý6sÄ©µÄËÙ¶ÈÇó³öËٶȼõΪÁ㻹ÐèµÄʱ¼ä£¬´Ó¶øµÃ³öÎïÌåÇ¡ºÃÍ£Ö¹µÄʱ¿Ì£®¸ù¾ÝËÙ¶ÈλÒƹ«Ê½·Ö±ðÇó³öABºÍBC¶ÎµÄ¾àÀ룬´Ó¶ø±È½Ï´óС£®

½â´ð ½â£ºA¡¢¸ù¾Ýͼ±íÖеÄÊý¾Ý£¬¿ÉÒÔÇó³öÎïÌåÏ»¬µÄ¼ÓËÙ¶È${a}_{1}=\frac{¡÷v}{¡÷t}=\frac{8}{2}m/{s}^{2}=4m/{s}^{2}$£¬ÔÚˮƽÃæÉϵļÓËÙ¶Èa₂=$\frac{¡÷v}{¡÷t}=\frac{8-12}{2}m/{s}^{2}=-2m/{s}^{2}$£¬¸ù¾ÝÔ˶¯Ñ§¹«Ê½£º8+a₁t₁+a₂t₂=12£¬t₁+t₂=2£¬½â³öt₁=$\frac{4}{3}s$£¬Öª¾­¹ý$\frac{10}{3}s$µ½´ïBµã£¬×î´óËÙ¶È${v}_{m}={a}_{1}t=4¡Á\frac{10}{3}m/s=\frac{40}{3}m/s$£¬¹ÊA´íÎó£¬BÕýÈ·£®
C¡¢´Ót=6sʱ¿ªÊ¼£¬ËٶȼõΪÁ㣬»¹ÐèµÄʱ¼ä$t¡ä=\frac{0-8}{-2}s=4s$£¬¼´t=10sʱ¿ÌÎïÌåÇ¡ºÃÍ£ÔÚCµã£¬¹ÊCÕýÈ·£®
D¡¢¸ù¾Ýv²-v₀²=2ax£¬Çó³öAB¶ÎµÄ³¤¶ÈΪ$\frac{200}{9}m$£¬BC¶Î³¤¶ÈΪ$\frac{400}{9}m$£¬ÔòA¡¢B¼äµÄ¾àÀëСÓÚB¡¢C¼äµÄ¾àÀ룬¹ÊDÕýÈ·£®
¹ÊÑ¡£ºBCD£®

µãÆÀ ½â¾ö±¾ÌâµÄ¹Ø¼üÕÆÎÕÔȱäËÙÖ±ÏßÔ˶¯µÄËÙ¶Èʱ¼ä¹«Ê½¡¢ËÙ¶ÈλÒƹ«Ê½£¬²¢ÄÜÁé»îÔËÓã¬Í¨¹ýÔȼÓËÙºÍÔȼõËÙÖ±ÏßÔ˶¯µÄ¼ÓËÙ¶ÈÒÔ¼°4sÄ©µÄËٶȣ¬½áºÏËÙ¶ÈÊǹ«Ê½Çó³öÎïÌåÔÚбÃæÉϵÄÔ˶¯Ê±¼äÊǹؼü£®