Jim records his physical training every time so that he can________it and think about how he should improve it the next day.
A:attach to
B:break up
C:refer to
D:keep on
“收入分配”是当今热点话题之一。当前,我国应坚持和完善的分配制度是( )
如图所示,将小砝码置于水平桌面上的薄纸板上,用水平向右的拉力将纸板迅速抽出,砝码的移动很小,几乎观察不到,这就是大家熟悉的惯性演示实验.若砝码和纸板的质量分别为m1和m2,各接触面间的动摩擦因数均为μ.重力加速度为g.要使纸板相对砝码运动,求所需拉力的大小的取值范围.