1、 1 1 P W t P Fv ( ) A P W t W t B P Fv C P Fv D P Fv D P W t P F v v P v P P F v 2 m t P t P ( ) A. P mg 2 t 2 P 1 2 mg 2 t 2B. P mg 2 t 2 P mg 2 t 2C. P 1 2 mg 2 t P mg 2 t D. P mg 2 t P 2mg 2 t C t P W t mg 1 2 gt 2 t 1 2 mg 2 t t P Fv mg gt mg 2 t C 4 7 6 3 4 7 6 ( ) A B C D C PG mgv v PG 4 m P0
2、a v P1 ( ) 2 A v B. P1 maC. P0v P1 mavD. P1v P0 mav C a F f ma P1 v f P1 v ma. F f vmax vmax P0 f P0v P1 mav C. 4 7 7 5 4 7 7 A B ( ) A B C PAPB D AC B mgh A (mgsin )s mg(ssin ) mgh A A B B v 2 B 2gh v 2 A 2(gsin )s 2g(ssin ) 2gh.A B D A PA (mgsin )vA B PB mgvB PAPB C 6 m F s v a F P ( ) AB F C v B
3、s A P Fv F 2 m t D 7 ( ) A B C D BC P v f ma a f v P A B F F s Ek C v at D 8 ( ) ( F kv 2 k ) P0 vm 2vm ( ) A 2P0 B k 43 C 8P0 D k 8 CD P0 Fvm F vm kv 2 m vm kv 3 m. 2vm P 8kv 3 m 8Po A C P0 P k 8k k k 8 B D 9 80 kW 20 m/s 2 t 2 m/s 2 (1) (2) (3) 3 3N (2)5 s (3)48 kW F f (1) F f a 0 v vm P Fv fvm f P vm 3 20N 3N. (2) F f ma F f ma 3 3 3N P Fvt Fat 3W t P F a 3 3 s 5 s. (3) 3 P3 F at3 3 48 kW. 10 4 7 8 1 kg F,1 s v t 4 7 8 (1) F (2) F 1 s (1)18 N (2)108 W (1) v t F a 6 m/s 2 . F ma 6 N. F F F ma a 12 m/s 2 F 18 N. (2) F l 1 2 a t 2 6 m F P Fl t 1W 108 W.
