Question

3£®ÄþÏÄ»Ø×å×ÔÖÎÇøÈËÃñÕþ¸®¹æ¶¨£º¸÷ÖÖ½ÚÈÕÈ翪ի½Ú£¬¹úÇì½Ú¡¢´º½ÚÆÚ¼ä¸ßËٶȹ«Â·ÔÝÍ£ÊÕ·Ñ£®Òò´Ë½»¹Ü²¿ÃŹ涨£¬ÉÏÊö³µÁ¾Í¨¹ýÊÕ·ÑÕ¾¿Úʱ£¬ÔÚרÓóµµÀÉÏ¿ÉÒÔ²»Í£³µÄ㨽»£©¿¨¶øÖ±½Ó¼õËÙͨ¹ý£®Èôij³µ¼õËÙÇ°µÄËÙ¶ÈΪv₀=20m/s£¬¿¿½üÕ¾¿ÚʱÒÔ´óСΪa₁=5m/s²µÄ¼ÓËÙ¶ÈÔȼõËÙ£¬Í¨¹ýÊÕ·ÑÕ¾¿ÚʱµÄËÙ¶ÈΪv_t=8m/s£¬È»ºóÁ¢¼´ÒÔa₂=4m/s²µÄ¼ÓËٶȼÓËÙÖÁÔ­À´µÄËٶȣ¨¼ÙÉèÊÕ·ÑÕ¾µÄÇ°¡¢ºó¶¼ÊÇƽֱ´óµÀ£©£®ÊÔÎÊ£º
£¨1£©¸Ã³µ¼ÝʻԱӦÔÚ¾àÊÕ·ÑÕ¾¿Ú¶àÔ¶´¦¿ªÊ¼¼õËÙ£¿
£¨2£©¸Ã³µ´Ó¼õËÙ¿ªÊ¼µ½×îÖÕ»Ö¸´µ½Ô­À´ËٶȵĹý³ÌÖУ¬Ô˶¯µÄʱ¼äÊǶàÉÙ£¿
£¨3£©ÔÚ£¨1£©£¨2£©ÎÊÌâÖУ¬¸Ã³µÒò¼õËٺͼÓËÙ¹ýÕ¾¶øµ¢ÎóµÄʱ¼äΪ¶àÉÙ£¿

Answer 1

·ÖÎö Õâ¸ö¹ý³ÌÊÇÓɼõËÙÔ˶¯ºÍ¼ÓËÙÔ˶¯×é³É£¬£¨1£©ÒÑÖª³õÄ©Ëٶȣ¬¼ÓËÙ¶ÈÓÃ${v}_{t}^{2}-{v}_{0}^{2}=2{a}_{1}{x}_{1}$Çó½â£¨2£©Óù«Ê½v=v₀+at·Ö±ðÇó½âʱ¼ä £¨3£©Çóʵ¼ÊÓÃʱÓëÔÈËÙͨ¹ýËùÓÃʱ¼äµÄ²îÖµ£®

½â´ð ½â£º£¨1£©¼õËÙ£º${v}_{t}^{2}-{v}_{0}^{2}=2{a}_{1}{x}_{1}$
8²-20²=2¡Á£¨-5£©x₁½âµÃ£ºx₁=33.6m
£¨2£©¼õËÙ£ºv_t=v₀+a₁t₁
8=20+£¨-5£©t₁½âµÃ£ºt₁=2.4s
¼ÓËÙ£ºv₀=v_t+a₂t₂
20=8+4t₂½âµÃ£ºt₂=3s
Ô˶¯µÄʱ¼ät=t₁+t₂=5.4s
£¨3£©¼ÓËÙ${v}_{0}^{2}-{v}_{t}^{2}=2{a}_{2}{x}_{2}$
20²-8²=2¡Á4x₂½âµÃ£ºx₂=42m
$t'=\frac{{x}_{1}+{x}_{2}}{{v}_{0}}=\frac{33.6+42}{20}=3.78s$
¡÷t=t-t'=5.4-3.78=1.62s
´ð£º£¨1£©¸Ã³µ¼ÝʻԱӦÔÚ¾àÊÕ·ÑÕ¾¿Ú33.6m´¦¿ªÊ¼¼õËÙ£»
£¨2£©¸Ã³µ´Ó¼õËÙ¿ªÊ¼µ½×îÖÕ»Ö¸´µ½Ô­À´ËٶȵĹý³ÌÖУ¬Ô˶¯µÄʱ¼äÊÇ5.4s£»
£¨3£©ÔÚ£¨1£©£¨2£©ÎÊÌâÖУ¬¸Ã³µÒò¼õËٺͼÓËÙ¹ýÕ¾¶øµ¢ÎóµÄʱ¼äΪ1.62s£®

µãÆÀ ¿¼²éÔȱäËÙÖ±ÏßÔ˶¯µÄ»ù±¾¹«Ê½£¬¶ÔÓÚ¸´ÔÓµÄÔ˶¯£¬ºÏÀíµÄÔËÓù«Ê½£¬¿ÉÒÔ±ÜÃâ½â·½³Ì£®