relative instantaneous centre

例句：

1. 1. The relative instantaneous centre of the system is at the point where the two forces are equal.
   系统的相对瞬时中心位于两个力相等的点上。
2. 2. The relative instantaneous centre of the system is at the point where the total force is zero.
   系统的相对瞬时中心位于总力为零的点上。
3. 3. The relative instantaneous centre of the system is at the point where the moment of inertia isa minimum.
   系统的相对瞬时中心位于转动惯量最小点的点上。