2019-2020
1
A
B
C
D
2 ( )
A1 1
B1 2
C1 2 3 2
D2 3 3 2
3 m
F
A
B
.
C mg
D
4 g = 10m/s 2
A 1s 10m/s B 1s 5m/s
C 1s 20m D 1s 10m
5
A
B
C
D
6 80N 100N
90N
A