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6、 5mg 5kD 7mg 5kA g F FNsin Fcos mg FNcos mg Fsin F 1 5 mg. F kx x mg 5k A. 2 2 m 0.4 kg v0 2 m/s F t 2 s A B A B L 10 m 3 3 . g 10 m/s 2 . (1) B (2) F F F 92492138 (1) a B v L v0t 1 2 at 2 v v0 at a 3 m/s 2 v 8 m/s. (2) FN Ff Fcos mgsin Ff ma Fsin FN mgcos 0 Ff N 11 F mg cos ma cos sin cos 3 3 sin 2 3 3 ) F 10 F Fmin 13 3 5N (1)3 m/s 28 m/s 13 3 5N
