fill in the blank: mvd.
两个质量为m速度为v的粒子沿着被某角度分开的平行线做相反方向的运动.角动量总值在任何原始出发点(都相等)
let the point be (x,y)
angular momentum of first particle = mvr1sin@ = mvp
angular momentum of second particle = mvr2sin@ = mvq
net angular momentum ( the angular momenta are in the same direction) = mvp+mvq =mvd (constant and independent of x and y)