(2)ÈôCE½×¶ÎÆôÓö¯Á¦»ØÊÕϵͳ,°Ñ»úеÄÜת»¯ÎªµçÄÜ,»ØÊÕЧÂÊΪ30%,Ôò¸Ã¶ÎСÆû³µ»¹ÄÜ»¬ÐжàÔ¶?
9.(2018Äê5ÔÂÎÂÖÝÊ®ÎåУÁªºÏÌå¸ß¶þÆÚÖÐÁª¿¼)ÈçͼËùʾ,Çᵯ»ÉÒ»¶ËÓëǽÏàÁ¬,ÖÊÁ¿Îª4 kgµÄľ¿éÑØˮƽÃæÒÔ4 m/sµÄËÙ¶ÈÏò×óÔ˶¯²¢Ñ¹Ëõµ¯»É,ľ¿éÀ뿪µ¯»ÉʱµÄ¶¯ÄÜΪ28.8 J,À뿪µ¯»ÉºóÓÖ
2
Ô˶¯ÁË3.6 m,gÈ¡10 m/s,Çó:
(1)ľ¿éÓëˮƽÃæ¼äµÄ¶¯Ä¦²ÁÒòÊý;
(2)µ¯»ÉÔÚ±»Ñ¹Ëõ¹ý³ÌÖеÄ×î´óµ¯ÐÔÊÆÄÜ;
(3)Áíһľ¿éÒÔ2 m/sµÄËÙ¶ÈѹËõµ¯»É,µ¯»ÉÔÚ±»Ñ¹Ëõ¹ý³ÌÖеÄ×î´óµ¯ÐÔÊÆÄÜÓëÇ°ÃæÏàͬ,Ôòľ¿éµÄÖÊÁ¿Îª¶àÉÙ?
10.ÈçͼËùʾΪˮÉÏ»¬Ìݵļò»¯Ä£ÐÍ:Çã½Ç¦È=37¡ãỬµÀABºÍˮƽ»¬µÀBCƽ»¬Á¬½Ó,ÆðµãA¾àË®ÃæµÄ¸ß¶ÈH=7 m,BC³¤d=2 m,¶ËµãC¾àË®ÃæµÄ¸ß¶Èh=1 m¡£ÖÊÁ¿m=50 kgµÄÔ˶¯Ô±´Ó»¬µÀÆðµãAµãÎÞ³õËÙµØ×ÔÓÉ»¬ÏÂ,Ô˶¯Ô±ÓëAB¡¢BC¼äµÄ¶¯Ä¦²ÁÒòÊý¾ùΪ¦Ì=0.1¡£ÒÑÖªcos 37¡ã=0.8,sin
2
37¡ã=0.6,Ô˶¯Ô±ÔÚÔ˶¯¹ý³ÌÖпÉÊÓΪÖʵã,gÈ¡10 m/s¡£Çó:
(1)Ô˶¯Ô±´ÓA»¬µ½BËùÐèµÄʱ¼ät;
(2)Ô˶¯Ô±µ½´ïCµãʱµÄËٶȴóСvC;
5
(3)±£³Öˮƽ»¬µÀ¶ËµãÔÚͬһÊúÖ±ÏßÉÏ,µ÷½Úˮƽ»¬µÀ¸ß¶ÈhºÍ³¤¶Èdµ½Í¼ÖÐB'C'λÖÃʱ,Ô˶¯Ô±´Ó»¬ÌÝƽÅ×µ½Ë®ÃæµÄˮƽλÒÆ×î´ó,Çó´Ëʱ»¬µÀB'C'¾àË®ÃæµÄ¸ß¶Èh'¡£
11.(2017Õã½Æß²ÊÑô¹âÁªÃËÆÚ³õÁª¿¼)Èçͼ¼×Ϊ»¬°åÔ˶¯,ÈçͼÒÒΪ»¬°å±ÈÈü»¬µÀʾÒâ¼òͼ,»¬ÐйìµÀ¾ùÔÚͬһÊúֱƽÃæÄÚ,б¹ìµÀABµÄÇã½Ç¦È=37¡ã,Óëˮƽ¹ìµÀBC¼äÓÃСԲ»¡Æ½»¬ÏàÁ¬(СԲ»¡µÄ³¤¶È¿ÉºöÂÔ)¡£Ð±¹ìµÀDEÇã½Ç¦Á=53¡ã,Óë°ë¾¶R=1.0 mµÄ¹â»¬Ô²»¡¹ìµÀEFGÏàÇÐÓÚEµã,FΪԲ»¡¹ìµÀ×îµÍµã,ÒÑÖªH1=4.2 m,L1=15.0 m,H2=1.0 m,H3=5.0 m¡£É軬°åÓëÖ±¹ìµÀ¼äµÄĦ²ÁÒòÊý¾ùΪ¦Ì=0.25,Ô˶¯Ô±Á¬Í¬»¬°åµÄ×ÜÖÊÁ¿m=60.0 kg¡£Ô˶¯Ô±´ÓAµãÓɾ²Ö¹¿ªÊ¼Ï»¬,´ÓCµãˮƽ·É³ö,ÓëбÃæDEÅöײºó,ûÓз´µ¯,¼ÌÐø»¬ÐÐ,¾¹ýÔ²»¡¹ìµÀFµãʱ¶Ô¹ìµÀѹÁ¦´óСΪFN=4 800 N,´ÓGµã·É³öºóÂäÔÚÓëGµãͬһˮƽÃæÇÒ¼ä¾àΪL2=6.0 mµÄKµã,¹ì¼£×î¸ßµãIÓëGKÃæµÄ¾àÀëH4=1.8 m¡£Ô˶¯Ô±Á¬Í¬»¬°å¿ÉÊÓΪÖʵã,ºöÂÔ¿ÕÆø×èÁ¦,sin 37¡ã=0.6,cos 37¡ã=0.8¡£Çó:
¼×
(1)Ô˶¯Ô±´ÓCµãˮƽ·É³öʱµÄËٶȴóСvC;
(2)Ô˶¯Ô±ÂäÔÚбÃæDEÉÏÓëбÃæÅöײ¹ý³ÌÖÐËðʧµÄ¶¯Äܦ¤Ek;
(3)GµãÓëÔ²ÐÄOµÄ¸ß¶È²î¦¤h¡£
12.(2018Äê2ÔÂÎÂÖÝÁùУÐ×÷Ìå¸ßÈýÆÚÄ©)ÉϺ£ÈÈ´ø·ç±©Ë®ÉÏÀÖÔ°ÓиöÏîÄ¿½Ð×ö¡°ÒôËÙ·ÉÁú¡±¡£Èçͼ¼×Ëùʾ,Á½Ìõ¸ßËÙ»¬µÀ,ÈË¿ÉÒÔÑöÎÔÏ»¬,Ï»¬Æð·ü¹²ÓÐ3²ã¡£Í¼ÒÒΪÆä¹ìµÀ²àÊÓͼ,ÖÊÁ¿Îª70 kgµÄÈË´ÓA´¦¾²Ö¹Ï»¬,¾BCDEF,×îÖÕÍ£ÔÚG´¦¡£ÒÑÖªAB¡¢BC¡¢CD¡¢DE¡¢EFÊǰ뾶Ϊ14 mµÄÔ²»¡,
2
Æä¶ÔÓ¦µÄÔ²ÐĽǾùΪ60¡ã,FG¶Îˮƽ¡£ÉèÈË»¬µ½FµãʱËÙ¶ÈΪ20 m/s,gÈ¡10 m/s,Çó:
6
(1)È˸ջ¬µ½Ô²»¡Ä©¶ËFµãʱ,»¬µÀ¶ÔÈËÊúÖ±ÏòÉϵÄ×÷ÓÃÁ¦F1µÄ´óС;
(2)ÔÚAF¶ÎÉÏ»¬¶¯¹ý³ÌÖÐÈË¿Ë·þ×èÁ¦Ëù×öµÄ¹¦Wf;
(3)ÈôÒ»¹â»¬Ð¡ÇòÔڸùìµÀÎÞˮʱ×ÔA´¦¾²Ö¹ÊÍ·Å,ÇÒ²»¼Æ¿ÕÆø×èÁ¦,СÇòÄÜ·ñÑØABCDEF¹ìµÀÔ˶¯?ÈôÄÜ,Çë˵Ã÷ÀíÓÉ;Èô²»ÄÜ,ÇëÇó³öСÇòÍÑÀë¹ìµÀµÄλÖü°Âä»Ø¹ìµÀËùÔÚµÄÔ²»¡²¿·Ö¡£
13.(2018Äê3ÔÂÉÜÐËÑ¡¿¼ÊÊÓ¦ÐÔ)ÈçͼΪÔÓ¼¼ÑÝÔ±½øÐÐĦÍгµ±íÑݵĹìµÀ,ËüÓÉÇãбֱÏß¹ìµÀAB¡¢Ô²»¡ÐιìµÀBCD¡¢°ëÔ²ÐιìµÀDE¡¢Ë®Æ½¹ìµÀEF×é³É,ÒÑÖª¹ìµÀABµÄÇã½Ç¦È=37¡ã,A¡¢B¼ä¸ß¶È²îH=12 m,¹ìµÀBCDµÄ°ë¾¶R=4.8 m,¹ìµÀDEµÄ°ë¾¶r=2.4 m,¹ìµÀ×îµÍµãC¾àˮƽµØÃæ¸ß¶È²îh=0.2 m,ÔÚ¹ìµÀABÉÏÔ˶¯Ê±Ä¦Íгµ(º¬ÈË)Êܵ½µÄ×èÁ¦ÎªÕýѹÁ¦µÄ,ÆäÓà×èÁ¦¾ù²»¼Æ¡£±íÑÝÕß´ÓAµã¼ÝʻĦÍгµÓɾ²Ö¹¿ªÊ¼ÑعìµÀABÔ˶¯,½Ó×ÅÑعìµÀBCDEFÔ˶¯,È»ºó´ÓFµãÀ뿪¹ìµÀ,×îºóÂäµ½µØÃæÉÏ
3
µÄGµã¡£ÒÑ֪ĦÍгµ¹¦ÂÊPºãΪ2¡Á10 W,·¢¶¯»ú¹¤×÷ʱ¼äÓɱíÑÝÕß¿ØÖÆ,±íÑÝÕßÓëĦÍгµ×ÜÖÊÁ¿m=100 kg,±íÑÝÕßÓëĦÍгµ¿ÉÊÓΪÖʵ㡣(cos 37¡ã=0.8)
(1)ij´Î±íÑÝÖÐ,ͨ¹ýCµãʱĦÍгµ¶Ô¹ìµÀµÄѹÁ¦Îª6 000 N,Çó¾¹ýCµãµÄËÙ¶ÈvC; (2)Âú×ã(1)ÖеÄÌõ¼þÏÂ,ÇóĦÍгµ·¢¶¯»úµÄ¹¤×÷ʱ¼ät;
(3)ÒÑÖª¡°ÊÜÁ¦Òò×Ók¡±µÈÓÚ±íÑÝÕßÓëĦÍгµÕûÌå³ÐÊܵÄѹÁ¦³ýÒÔÕûÌåµÄÖØÁ¦,ÔÚk¡Ü8Ìõ¼þϱíÑÝÕßÊÇ°²È«µÄ,ÇóÄÜÔÚ°²È«Íê³ÉÍêÕû±íÑݵÄÇé¿öÏÂ,±íÑÝÕßÂäµãGµãÓëFµãµÄˮƽ¾àÀëµÄ¿ÉÄÜÖµ¡£
7
ÌáÉýѵÁ·7 ¶¯Äܶ¨ÀíµÄÓ¦ÓÃ
1.´ð°¸ (1)5 m/s (2)-2.1¡Á104
J (3)1.85 s ½âÎö (1)Æû³µÑØÍäµÀ1ÐÐÊ»µÄ×î´óËÙ¶ÈΪv1,ÓÐ
kmg=m
µÃv1==5 m/s¡£
(2)Æû³µÑØÍäµÀ2ÐÐÊ»µÄ×î´óËÙ¶ÈΪv2,ÓÐkmg=m
µÃv2==5 m/s
Ö±µÀÉÏÓɶ¯Äܶ¨ÀíÓÐP¡¤t-mgh+Wf=
´úÈëÊý¾Ý¿ÉµÃW2.1¡Á104
f=- J¡£ (3)
=1.25mg?v=
¿ÉÖªrÔö´óvÔö´ó,r×î´ó,Çл¡³¤×îС,¶ÔӦʱ¼ä×î¶Ì,ËùÒԹ켣Éè¼ÆÓ¦ÈçÓÒͼËùʾ ÓÉͼ¿ÉÒԵõ½r'2
=+r'-2
´úÈëÊý¾Ý¿ÉÒԵõ½r'=12.5 m Æû³µÑØן÷ÏßÐÐÊ»µÄ×î´óËÙ¶Èv'==12.5 m/s
ÓÉsin¦È==0.8¿ÉÖª,¶ÔÓ¦µÄÔ²ÐĽǶÈ2¦È=106¡ã
Ïß·³¤¶Ès=¡Á2¦Ðr'
×î¶Ìʱ¼ät'=¡Ö1.85 s¡£
2.´ð°¸ (1)3 m/s (2)Ë®ÔÚBµãÊܵ½¹ÜµÀÊúÖ±ÏòϵÄѹÁ¦,Ϊ0.8 N (3)49.2 W ½âÎö (1)Ë®×öƽÅ×Ô˶¯,ÊúÖ±·½Ïòh=R+Rcos¦È=1.6 m ¸ù¾Ý=2gh
µÃvCy=4
m/s
ÓÖÒòΪˮÔÚCµã¸ÕºÃÓëÔ²ÏàÇÐ,ËùÒÔtan¦È=
ËùÒÔvB=3
m/s ¡£
(2)ÒÔС¶ÎˮΪÑо¿¶ÔÏó¡£µ±Ë®ÔÚ×î¸ßµãBÊܵ½µÄ¹ÜµÀ×÷ÓÃÁ¦ÊÇ0ʱ,ÓÐFn=mg=m
vÁÙ=
m/s<3 m/s
¹ÊË®ÔÚBµãÊܵ½¹ÜµÀÊúÖ±ÏòϵÄѹÁ¦,
mg+FN=m µÃFN=0.8 N¡£
(3)ÒÔµ¥Î»Ê±¼ä(t=1 s)´ÓBµãÅç³öµÄˮΪÑо¿¶ÔÏó, m0=¦ÑSvBt
ÓÉÄÜÁ¿Êغ㶨ÂɿɵÃ,ÒÔA´¦ÎªÊÆÄÜÁãµãÓÐ
Pt=m0g(2R)+m0
µÃP=34.8
W¡Ö49.2 W¡£
8