A:what I was doing
B:what was I doing
C:what I am doing
D:what am I doing
物理量
1
2
3
钩码重G(N)
4
6
钩码上升高度h(m)
0.1
绳端拉力F(N)
1.8
1.4
2.4
绳端移动距离S(m)
0.3
0.5
机械效率η
74%
①
②
实验室制取乙烯和石油分馏的实验操作,下列说法正确的是( )