momentum vector meaning in Chinese

动量矢量
力矩矢量

Orbital angular momentum vector
轨道角动量矢量
In the motion , the direction of angular momentum vector changes every moment , because there is a torque caused by gravity act on the wheel , then the wheel rotate itself and rotate around the fixed point
车轮进动实验：在进动中，角动量的矢量方向不断改变，是因为受到一个由重力产生的力矩，使车轮在自转的同时又绕支点转动。