A:600
B:1200
C:1800
D:2400
The naughty boy is always in his room.His mother is very angry.
卷柏又名九死还魂草,有根、茎、叶,无花、果实、种子,据此判断卷柏属于( )
试验次数
1
2
钩码重G/N
4
钩码上升高度h/m
0.1
绳端拉力F/N
1.8
1.6
绳端移动的距离s/m
0.3
0.4
机械效率η
74.1%