Question

4£®Ò»¸öÖÊÁ¿ÎªlkgµÄСÇòÒÔÒ»¶¨µÄ³õËÙÊúÖ±ÏòÉÏÅ׳ö£¬×îÖÕÂä»ØÅ׳öµã£¬¼ÙÈçСÇòËùÊÜ¿ÕÆø×èÁ¦´óСºã¶¨£¬¸Ã¹ý³ÌµÄλÒÆһʱ¼äͼÏóÈçͼËùʾ£¬g=l0m/s²£¬ÏÂÁÐ˵·¨ÕýÈ·µÄÊÇ£¨¡¡¡¡£©

• A£® СÇòÅ׳öʱµÄËÙ¶ÈΪ6m/s
• B£® СÇò´Ó×î¸ßµãÏÂÂäµ½´¦·¢µã¹ý³ÌËùÓõÄʱ¼äΪ$\frac{{\sqrt{6}}}{2}$s
• C£® СÇòÏÂÂäµ½Å׳öµã¹ý³ÌÖеļÓËÙ¶ÈΪ8m/s²
• D£® СÇòÉÏÉý¹ý³ÌµÄƽ¾ùËÙÂʵÈÓÚϽµ¹ý³ÌµÄƽ¾ùËÙÂÊ

Answer 1

·ÖÎö ¸ù¾ÝͼÏó¶Á³öÉÏÉý¹ý³ÌµÄλÒƺÍʱ¼ä£¬ÇóµÃƽ¾ùËٶȣ¬Óɹ«Ê½$\overline{v}=\frac{{v}_{0}^{\;}+v}{2}$Çó½â³õËٶȣ¬ÓÉËٶȹ«Ê½Çó³öÉÏÉýʱµÄ¼ÓËٶȣ¬ÓÉÅ£¶ÙµÚ¶þ¶¨ÂÉÇó³ö¿ÕÆø×èÁ¦£¬ÔÙÓÉÅ£¶ÙµÚ¶þ¶¨ÂÉÇóµÃÏÂÂäʱµÄ¼ÓËٶȣ¬¼´¿ÉÓÉλÒƹ«Ê½ÇóÏÂÂäʱ¼ä£¬¸ù¾Ýƽ¾ùËÙÂʵĶ¨Òå±È½ÏÉÏÉýºÍϽµµÄƽ¾ùËÙÂÊ£®

½â´ð ½â£ºA¡¢Ð¡ÇòÉÏÉýµÄλÒÆ${x}_{1}^{\;}=6m$£¬ÓÃʱ${t}_{1}^{\;}=1s$£¬Æ½¾ùËÙ¶È$\overline{{v}_{1}^{\;}}=\frac{{x}_{1}^{\;}}{{t}_{1}^{\;}}=\frac{6}{1}m/s=6m/s$£¬ÓÉ$\overline{v}=\frac{{v}_{0}^{\;}+v}{2}=\frac{{v}_{0}^{\;}+0}{2}$£¬µÃ³õËÙ¶È${v}_{0}^{\;}=12m/s$£¬¹ÊA´íÎó£»
BCD¡¢ÉÏÉýʱ¼ÓËٶȴóСΪ${a}_{1}^{\;}=\frac{{v}_{0}^{\;}}{{t}_{1}^{\;}}=\frac{12}{1}m/{s}_{\;}^{2}=12m/{s}_{\;}^{2}$£¬ÓÉÅ£¶ÙµÚ¶þ¶¨ÂÉ£º$mg+f=m{a}_{1}^{\;}$£¬½âµÃ¿ÕÆø×èÁ¦µÄ´óСf=2N
¶ÔÓÚÏÂÂä¹ý³Ì£¬ÓÉÅ£¶ÙµÚ¶þ¶¨ÂɵÃ$mg-f=m{a}_{2}^{\;}$£¬½âµÃ${a}_{2}^{\;}=8m/{s}_{\;}^{2}$£¬¹ÊCÕýÈ·£»
¸ù¾ÝλÒƹ«Ê½$x=\frac{1}{2}{a}_{2}^{\;}{t}_{2}^{2}$£¬´úÈëÊý¾ÝµÃÏÂÂä¹ý³ÌµÄʱ¼ä${t}_{2}^{\;}=\frac{\sqrt{6}}{2}s$£¬¹ÊBÕýÈ·£»
¸ù¾Ýƽ¾ùËÙÂʵĹ«Ê½$v=\frac{s}{t}$£¬ÉÏÉýºÍ¹ý³ÌµÄ·³ÌÏàµÈ£¬Ê±¼ä²»µÈ£¬ËùÒÔÉÏÉý¹ý³ÌµÄƽ¾ùËÙÂʲ»µÈÓÚϽµ¹ý³ÌµÄƽ¾ùËÙÂÊ£¬¹ÊD´íÎó£»
¹ÊÑ¡£ºBC

µãÆÀ ½â¾ö±¾ÌâµÄ¹Ø¼üÒªÊìÁ·ÔËÓÃÔ˶¯Ñ§¹«Ê½ºÍÅ£¶ÙµÚ¶þ¶¨ÂÉÑо¿ÉÏÉýÓëÏÂÂä¹ý³ÌµÄ¼ÓËٶȡ¢Ô˶¯Ê±¼ä£¬ÒªÖªµÀ¶ÔÓÚÔȱäËÙÖ±ÏßÔ˶¯£¬Çóƽ¾ùËÙ¶ÈÓÐÁ½¸ö¹«Ê½$\overline{v}=\frac{x}{t}$ºÍ$\overline{v}=\frac{{v}_{0}^{\;}+v}{2}$£®¶ÔÓÚÉÏÉýºÍÏÂÂä¹ý³Ì£¬ÒªÃ÷ȷλÒÆ´óСÏàµÈ£¬¿ÕÆø×èÁ¦´óСÏàµÈ£®