1、 10 3 30 12012 7 18 30 A B C D A 2 2000 kg A 5m/s 2B 1 10 4 N C 480m D 40m/s C 3 vt OPQ OQT 1 s 2 s 21 ss 0 s A 1 B 01 ss 2 C 2 0 s s 2 D 02 ss 1 B T 2 s 2 1 s s 1 0 s s T A 1 0 s s T 2 B C 1 2 s s 1 0 s s 2 0 s s D 4 T T 2 C 5 =30 G F F F F f F f A 33 , 63 F G f G B 33 , 24 F G f G C G f G F 4 3 ,
2、3 3 D G f G F 6 3 , 3 3 D F 2 G G F f 6 3 60 cos 3 3 2 cos C D : # # F 6 F t g A.g B.2g C.3g D.4g B 7 B A A F F t F=kt k f A B B V-t B B 8. m A k B B a A B F A k mgB k maC A D K F 2 2 ACD A A B x kx mg F mg kx k mg x A B A A C k g m k mg k kx W 2 ) ( 2 1 2 1 2 2 2 2 F D B 9 x O M q 1 q 2 x A B BD C
3、A q 1 q 2 B BD C x C A C D B D A x 10 A,B U A B , q, m, h A B c A. B. B 2h A C. U A C D. U A A B B 6 4 24 2 0 11 A B A B A B C B D B AD 12 A A B B F F B F 1 B A F 2 A F 3 A F 4 F A F 1 F 4 B F 1 F 4 C F 2 F 3 D F 2 F 3 BC B 13. m 2m 3m 2m 3m T F 3m A 2m B F T C F T 5 . 1 D m 2m 3 / 2T AC 2m m 2m m 2
4、m 5 A m 2m m T m m T a m 3 2 F F T a m m m F m 2 3 2 B C m 2m m 3 ) 3 ( T m T m ma f m D 14. R R a b m v a b : # # A b a b 5mg B gR v 5 b C v gR 5 D gR v 5 a b 6mg : , , BD C mg R v m F 2 1 1 mg R v m F 2 2 2 2 2 2 1 2 1 2 2 1 mv R mg mv mg F F 6 1 2 D 15 M 1kg v 0 =4m/s A B L=6m, v =2m/s 0.2 A 2m/s
5、 B 4s C 6 D 18 ABD m vt l 2 2 2 J s l f Q 2 1 2 2 18J D 16 +10-2C A B 0.1J A 10V A B 0V B C. 1 D 2 ABC 2 22 17. 6 A B C D E F G 7 4 220 V 50 Hz : , , 1 T F v F v F _ 2 T=0.02s a _ m/s 2 3 210 V _ 1 T d d v F 10 4 6 2 2 / 51 . 0 s m 3 18 8 NQ PQ 1 2 K d K t 1 t 2 1 d t 1 t 2 _ a=_ 2 M m M m _ : 3 M m _ 1 x t d t d a 2 ) ( ) ( 2 1 2 2 2 Ma mg m M mg mg 3 m M 19. _ 20. k 1 m 1 m 2 1 2 k 2 2 1 1 ) 1 1 ( ) ( 2 1 2 2 1 1 k k g m m m 1 k 1 1 1 k g m x 2 k 2 2 1 2 k g m g m x 2 2 x 2 1 2 3 k g m x 1 ) 1 1 ( ) ( ) ( 2 1 2 2 1 1 3 2 1 1 k k g m m m x x x g m
