1、 1 1 1 1 1 2 W Flcos_ F l l 3 2 1 2 3 2 (1)P W t P t (2)P Fvcos ( F v ) v P v P 4 (1) (2) 1 (1) (2) (3) (4) (5) P Fv (6) 2 a b c d M F F F ( ) A Wa B Wd C WaWc D D F W Flcos F D 3 ( ) m a m m ( ) 3 A B C D ACD a gtan agtan a4WF1 Wf22Wf1 B WF24WF1 Wf2 2Wf1 C WF2 F2 2 W Fl Wf1 1 2 Wf2 WF1 1 4 WF2 C A
2、B D WG mg h 6 F x F F1 F2 2 W F xcos W Ffs P W Pt F W Fs W qU 1. (1) P W t . (2) P F v cos v 2 (1) P F vcos v t (2) P F vF vF v F (3) P Fv v Fv F v 1. v A B ( ) A B C D B G F O 7 F G tan (F G ) F Gtan F v F P Fvcos Gvsin . A B F B A C D 2 ( ) 1 kg t 0 F ( ) 92492212 A 0 2 s 4 W B 2 s 4 J C 2 s D 1 s
3、 2 s AD 1 s v1 F1 m t1 3 1 3 m/s. 2 s v2 v1 F2 m t2 (3 1 1 1)m/s 4 m/s. 2 s W2 1 2 mv 2 2 1 2 mv 2 1 3.5 J 0 2 s P 1 2 mv 2 2 t 2 2 W 4 W. A B 1 s P1 F1v1 9 W 2 s P2 F2v2 4 W P1 P2 C D 1 8 P t v t O A v F P v a F F m a F F m F v P Fv P Fv1 t0 v1 aA B F F a 0 F P vmv F P v a F F m vm BC F F a 0 vm P
4、F 2. (1) vm P Fmin P F ( Fmin F ) (2) v P F vm P F . (3) W Pt. Pt F s Ek. 8 4kg. 7W 7W 0.1 (g 10 m/s 2 ) (1) 9 (2) A B 7W( ) B 0. AB 4m A B (1) P1m fvm vm P1m f f mg 5N P1m 7W vm 60 m/s. (2) 7W( ) vm P1m P2m f vm 100 m/s C A C t1 AC x1 C B t2 CB x2 CB a M 8m 5kg C B Ff Ma a f M 0.1Mg M 1 m/s 2vm at2
5、 t2 vm a 100 s x2 vm 2 t2 x2 3m x1 xAB x2 4m A C (P1m P2m)t1 f x1 1 2 Mv 2 m t1 500 s t t1 t2 600 s. (1)60 m/s (2)600 s 10 1 1. m 3kg a 0.2 m/s 2 vm 1.02 m/s g 10 m/s 2 (1) (2) (3) 2 s (1) Pm Fvm F mg Pm mg vm 4W. (2) t1 v1 F1 mg ma Pm F1 v1 v1 at1 t1 5 s. (3)2 s v2 at2 2 s P F1 v2 P 4W. 4W (2)5 s 4
6、W 2 2 ) 3kg 2 000 N 4W a 1 m/s 2 (g 10 m/s 2 ) (1) t1 (2) (3) 143.5 m 92492213 (1) F mg Ff ma 11 v P Fv v at1 t1 7 s. (2) vm a 0 P (mg Ff)vm vm 8 m/s. (3) x1 1 2 at 2 1 Pt2 (mg Ff)x2 1 2 mv 2 m 1 2 mv 2 x x1 x2 t2 15 s t t1 t2 22 s. (1)7 s (2)8 m/s (3)22 s 1 W Pt W Fl ( F ) 2 W Fl W Pt ( P ) 3 P Fv F P Ffvm
