Question

9£®Ð¡½Î³µ´Ó¸ßËÙ¹«Â·µÄ³ö¿ÚA½øÈëÔѵÀ£¬ÏÈÔȼõËÙÖ±Ïßͨ¹ýÏÂÆ·¶ÎÖÁBµã£¨Í¨¹ýBµãÇ°ºóËÙÂʲ»±ä£©£¬ÔÙÔÈËÙÂÊͨ¹ýˮƽԲ»¡Â·¶ÎÖÁCµã£¬×îºó´ÓCµãÑØƽֱ·¶ÎÔȼõËÙµ½ÊÕ·ÑÕ¾Dµãͣϣ®ÒÑÖª½Î³µÔÚAµãµÄËÙ¶Èv₀=72km/h£¬AB³¤L₁=75m£»BC¶ÎΪ°ë¾¶R=20mµÄËÄ·Ö֮һˮƽԲ»¡¶Î£¬ÂÖÌ¥ÓëBC¶Î·Ãæ¼äµÄ¶¯Ä¦²ÁÒòÊý¦Ì=0.5£¬×î´ó¾²Ä¦²ÁÁ¦¿ÉÈÏΪµÈÓÚ»¬¶¯Ä¦²ÁÁ¦£¬CD¶ÎΪƽֱ·¶Î³¤L₂=50m£¬ÖØÁ¦¼ÓËÙ¶ÈgÈ¡l0m/s²£®Çó£º
£¨1£©Èô½Î³µµ½´ïBµãËٶȸպÃΪv=36km/h£¬Çó½Î³µÔÚABÏÂƶεļÓËٶȵĴóС£»
£¨2£©½Î³µAµãµ½DµãÈ«³ÌµÄ×î¶Ìʱ¼ä£®

Answer 1

·ÖÎö £¨1£©½Î³µÔÚAB¶Î×öÔȼõËÙÖ±ÏßÔ˶¯£¬ÒÑÖª³õËٶȡ¢Î»ÒƺÍÄ©Ëٶȣ¬¸ù¾ÝËÙ¶ÈλÒƹØϵ¹«Ê½Çó½â¼ÓËٶȣ»
£¨2£©·ÖÈý¶Î£¬·Ö±ðÓÉÔ˶¯Ñ§¹«Ê½Çó½âʱ¼ä£¬¼´¿ÉµÃµ½×Üʱ¼ä£®

½â´ð ½â£º£¨1£©ABÏÂÆ¶Σ¬¸ù¾ÝËÙ¶ÈλÒƹØϵÓУº${v}^{2}-{v}_{0}^{2}=-2{a}_{1}{L}_{1}$
½âµÃ£º${a}_{1}=\frac{{v}_{0}^{2}-{v}^{2}}{2{L}_{1}}=\frac{2{0}^{2}-1{0}^{2}}{2¡Á75}m/{s}^{2}=2m/{s}^{2}$
£¨2£©Æû³µÔÚBC¶Î×öÔ²ÖÜÔ˶¯£¬Ç¡ºÃËÙ¶È×î´óʱ£¬×î´ó¾²Ä¦²ÁÁ¦ÌṩÏòÐÄÁ¦£¬ÓУº$¦Ìmg=m\frac{v{'}^{2}}{R}$
´úÈëÊý¾Ý½âµÃ£ºv'=10m/s¡¡
ÉèAB¶Îʱ¼äΪt₁£¬BC¶Îʱ¼äΪt₂£¬CD¶Îʱ¼äΪt₃£¬È«³ÌËùÓÃ×î¶Ìʱ¼äΪt£®
${L}_{1}=\frac{{v}_{0}+v'}{2}{t}_{1}$£¬½âµÃ£ºt₁=5s
$\frac{1}{2}¦ÐR=v'{t}_{2}$£¬½âµÃ£ºt₂=3.14s
${L}_{2}=\frac{1}{2}v'{t}_{3}$£¬½âµÃ£ºt₃=10s
Ôò£ºt=t₁+t₂+t₃=18.14s
´ð£º£¨1£©½Î³µÔÚABÏÂƶεļÓËٶȵĴóСΪ2m/s²£»
£¨2£©½Î³µAµãµ½DµãÈ«³ÌµÄ×î¶Ìʱ¼äΪ18.14s£®

µãÆÀ ±¾ÌâÊÇÔ˶¯Ñ§Ó붯Á¦Ñ§×ÛºÏÌ⣬ÄܽáºÏÎïÌåµÄÔ˶¯Çé¿ö£¬Áé»îÑ¡ÔñÔ˶¯Ñ§µÄ¹«Ê½ÐÎʽÊǹؼü£¬µ±²»Éæ¼°¼ÓËٶȶøÒªÇóʱ¼äʱ£¬¿ÉÓÃλÒƵÈÓÚƽ¾ùËٶȳËÒÔʱ¼äÀ´Çó£®