µÚÒ»Õ ¸ßÖÐÎïÀí¾ºÈüºÍ¸ß¿¼Á¦Ñ§Ï°Ìâ½â´ð(Å£¶Ù¶¨ÂÉ¡¢¶¯Á¿¶¨Àí ¶¯Á¿Êغ㶨ÂÉ) ÏÂÔØ±¾ÎÄ

ÉèÆøÇòµÄ¼ÓËÙ¶Èa£¬Ôò

½á¹ûͬÉÏ¡£

18. 70kgÖØµÄÈ˺Í210kgÖØµÄС´¬×î³õ´¦ÓÚ¾²Ö¹¡£ºóÀ´ÈË´Ó´¬ºóÏò´¬Í·ÔÈËÙ×ßÁË3.2mÍ£ÏÂÀ´¡£ÎÊ´¬ÏòÄĸö·½ÏòÔ˶¯£¬Òƶ¯Á˼¸Ã×£¿²»¼Æ´¬ËùÊܵÄ×èÁ¦¡£

Ma?m(am?a)d2MxM?mxmac?2()?dtM?mM?mmam?a?M?m

mamF?(M?m)g?(M?m)(a?)M?m µÃ£º

F?mama??gM?m

£¨2£©ÖʵãµÄ¶¯Á¿¶¨Àí

??d?p,?FÍâ?dt

F?F?£¨M?m)g Òò?Íâ??d?pd?(MvM?mvm)?FÍâ?dtdt?Ma?m(a?am) µÃ£ºF?(M?m)g?(M?m)a?mam

F?mama??gM?m

½â£¬ÒÔµØÃæÎª²ÎÕÕϵ£¬È˵Äǰ½ø·½ÏòÎª×ø±êÖáµÄÕý·½Ïò¡£ÏµÍ³Ë®Æ½·½Ïò¶¯Á¿Êغ㡣

19.ÅÚ³µ¹Ì¶¨ÔÚ³µÏáÄÚ£¬×î³õ¾ù´¦ÓÚ¾²Ö¹¡£ÏòÓÒ·¢Éäһöµ¯Í裬³µÏáÔòÏò×óÔ˶¯¡£µ¯ÍèÉäÔÚ¶ÔÃæÇ½ÉϺóËæ¼´Ë³Ç½±ÚÂäÏ¡£Îʴ˹ý³ÌÖгµÏáÒÆ¶¯µÄ¾àÀëÊǶàÉÙ£¿ÒÑÖªÅÚ³µºÍ³µÏá×ÜÖÊÁ¿ÎªM£¬µ¯ÍèÖÊÁ¿Îªm,ÅÚ¿Úµ½¶ÔÃæÇ½ÉϵľàÀëΪL¡£²»¼ÆÌú¹ì×÷ÓÃÓÚ³µÏáµÄ×èÁ¦¡£

??mv?MV?0£¬

?x1?x2m?M?0?t?t m?x1?M?x2?0£¬

m(3.2??x2)?M?x2?0£¬

3.2m?x2???0.8(m)M?m

½â£¬ÒÔµØÃæÎª²ÎÕÕϵ£¬Ë®Æ½ÏòÓÒÎª×ø±êÖáÕý·½Ïò¡£

ϵͳÔÚˮƽ·½Ïò¶¯Á¿Êغ㡣

É赯ÍèµÄËÙ¶ÈΪv,³µÏáµÄËÙ¶ÈΪV£¬³µÏáÒÆ¶¯µÄ¾àÀëΪs£¬Ô˶¯

µÄʱ¼äΪt£¬ÔòµÃ

mv?MV?o

L?ss?v?,V?,tt L?ss?m?M?0,tt

m(L?s)?Ms?o,mLs?M?m

ÓÉÖÊÐÄÔ˶¯¶¨Àí£ºË®Æ½·½ÏòϵͳµÄÖÊÐIJ»¶¯¡£

MxM?mxmM(xM?s)?m(xm?L?s)?M?mM?m µÃ£¬0??Ms?mL?ms,

mLs?M?m£¬½á¹ûͬÉÏ¡£

20.ÔØÈ˵ÄÇÐŵ»ùºÍÉ£ËþÄÉÆû³µÖÊÁ¿¸÷Ϊm1=165¡Á10kgºÍm2=115¡Á10kg,¸÷ÒÔËÙÂÊv1=90km/hºÍv2=108km/hÏò¶«ºÍÏò±±ÐÐÊ»¡£ÏàײºóÁªÔÚÒ»Æð»¬³ö¡£Ç󻬳öµÄËÙ¶È¡£²»¼ÆÄ¦²Á£¨ÇëÓÃÖÊÐIJÎÕÕϵÇó½â£©¡£

½â£¬ÓÃÖÊÐIJÎÕÕϵÇó£¬Öʵã×é¶ÔÖÊÐIJÎÕÕϵµÄ¶¯Á¿×ÜΪÁã¡£ ÖÊÐÄϵµÄËÙ¶È£º

m1dx1m1vcx???90?53.1(km/h)m1?m2dtm1?m2m1dy2m1vcy???108?44.4(km/h)m1?m2dtm1?m2

Á½³µµÄÖÊÐÄËÙ¶È£º

?vc?53.1?i?44.4?j vc?69(km/h)

m2vcytg??,m1vcx¿ÉÇó¡£

21.һöÊÖÁñµ¯Í¶³ö·½ÏòÓëˮƽ·½Ïò³É450,Ͷ³öµÄËÙÂÊΪ25m/s£¬ÔÚ¸ÕÒª½Ó´¥Óë·¢ÉäµãÍ¬Ò»Ë®Æ½ÃæµÄÄ¿±êʱ±¬Õ¨£¬Éè·Ö³ÉÖÊÁ¿ÏàµÈµÄÈý¿é£¬Ò»¿éÒÔËÙ¶Èv3Ǧֱ³¯Ï£¬Ò»¿é˳±¬Õ¨´¦ÇÐÏß·½ÏòÒÔv2=15m/s·É³ö£¬Ò»¿éÑØ·¨Ïß·½ÏòÒÔv1·É³ö¡£Çóv1ºÍv3£¬²»¼Æ¿ÕÆø×èÁ¦¡£

½â£¬ÄÚÁ¦Ô¶Ô¶´óÓÚÍâÁ¦£¬Öʵã×鶯Á¿Êغ㡣