守恒质量

conserve cash───节约现金

center of mass───[力]质心；质量中心

condemned man───死刑犯

conserve fuel───节约燃料

conserved───adj.保守的；v.保存；保全（conserve的过去式）

conserves───蜜饯

consecratedness───神圣

clearly, mass is conserved, not mole Numbers.───显然是质量守恒，而不是摩尔数守恒。

The velocity of the center of mass has not changed as seen from your frame of reference, because the velocity of center of mass is always the same, remember, because momentum is conserved.───质量重心的速度，并没有发生改变，你在参照系中可以看出，因为质量重心的速度，总是保持不变，要记住，由于动量守恒。