2019-2020
1 8cm 4N 10cm
A400 m/N B50 N/m C200 N/m D200 m/N
2 ,
A ,
B
C ,
D
3
A B
C D
4
( )
A 20s B 20s
C 20s D 20s
5 8 s
4 s
( )
A a1a2 21
B v1v2 21
C a1a2 12
D x1x2 21
6
A
B
C
D
7 .
M N .
