Question

15£®Ä³Ñ§Ï°Ð¡×é×öÁËÇáÖØÎïÌåÔÚ¿ÕÆø»·¾³ÏÂÂäµÄ¶Ô±ÈʵÑ飺ÔÚ´óÂ¥µÄÑǫ̂±ßͬ¸ß¶È¡¢Í¬Ê±¾²Ö¹ÊÍ·ÅСÌúÇòÓëӲֽƬ£¬ÂäÖÁһ¥ˮƽ²ÝµØÉÏ£¬¹Û²ìµ½Ð¡ÌúÇòÏÈÂäµØ£¬²¢²â³öËüÃÇÏÂÂäµÄʱ¼ä·Ö±ðΪt₁=2.0s¡¢t₂=3.0s£®Èô¼ÙÉèСÌúÇòËùÊܵĿÕÆø×èÁ¦ºöÂÔ²»¼Æ£¬Ó²Ö½Æ¬ËùÊܵĿÕÆø×èÁ¦´óС²»±ä£®ÖØÁ¦¼ÓËÙ¶ÈgÈ¡10m/s²£®Çó£º
£¨1£©Ð¡ÌúÇòÏÂÂäµÄ¸ß¶È£»
£¨2£©Ó²Ö½Æ¬ÏÂÂä¹ý³ÌµÄ¼ÓËٶȴóС£»
£¨3£©Ó²Ö½Æ¬ÏÂÂä¹ý³ÌËùÊÜ¿ÕÆø×èÁ¦µÄ´óСÓëÆäÖØÁ¦µÄ±ÈÖµ£®

Answer 1

·ÖÎö £¨1£©Ð¡Ìú¿é×ö×ÔÓÉÂäÌåÔ˶¯£¬ÓÉλÒÆʱ¼ä¹«Ê½ÇóµÄ¸ß¶È£»
£¨2£©ÓÉλÒÆʱ¼ä¹«Ê½ÇóµÄ¼ÓËٶȣ»
£¨3£©ÓÉÅ£¶ÙµÚ¶þ¶¨ÂÉÇóµÄ×èÁ¦£¬¼´¿ÉÇóµÃËùÊÜ¿ÕÆø×èÁ¦µÄ´óСÓëÆäÖØÁ¦µÄ±ÈÖµ£®

½â´ð ½â£º£¨1£©Ð¡ÌúÇò×ö×ÔÓÉÂäÌåÔ˶¯£¬¹ÊÏÂÂäµÄ¸ß¶ÈΪ£º
h=$\frac{1}{2}{gt}_{1}^{2}=\frac{1}{2}¡Á10¡Á{2}^{2}m=20m$
£¨2£©ÓÉh=$\frac{1}{2}a{t}^{2}$µÃ£º
a=$\frac{2h}{{t}_{2}^{2}}=\frac{2¡Á20}{{3}^{2}}m/{s}^{2}=\frac{40}{9}m/{s}^{2}$
£¨3£©ÓÐÅ£¶ÙµÚ¶þ¶¨ÂÉ¿ÉÖª
mg-f=ma
f=mg-ma=$\frac{50}{9}m$
¹Ê$\frac{f}{mg}=\frac{5}{9}$
´ð£º£¨1£©Ð¡ÌúÇòÏÂÂäµÄ¸ß¶ÈΪ20m£»
£¨2£©Ó²Ö½Æ¬ÏÂÂä¹ý³ÌµÄ¼ÓËٶȴóСΪ$\frac{40}{9}m/{s}^{2}$£»
£¨3£©Ó²Ö½Æ¬ÏÂÂä¹ý³ÌËùÊÜ¿ÕÆø×èÁ¦µÄ´óСÓëÆäÖØÁ¦µÄ±ÈֵΪ$\frac{5}{9}$£®

µãÆÀ ±¾ÌâÖ÷Òª¿¼²éÁËÅ£¶ÙµÚ¶þ¶¨ÂÉÓëÔ˶¯Ñ§¹«Ê½£¬¼ÓËÙ¶ÈÊǹؼü