在D因子作用下分解的是
A．C3bBB．C3bBbC．C3．BD．βIHE．C5678(9)n
参考答案：C
如图所示，不计重力的杠杆OB可绕O点转动，重为6N的重物P悬挂在杠杆的中点A处，拉力F与杠杆成30°角，杠杆在水平位置保持平衡。
（1）请在图中画出拉力F的力臂；
（2）求出拉力的大小F=_____N。
Beer is the most popular drink among male drinkers which overall consumption is significantly higher than that of women.
