“向心力演示器”结构简单，易操作，能形象直观地演示归纳出向心力与质点的质量、角速度及圆半径的关系，是一种很实用的教学仪器．在做演示实验时，我们发现该仪器也有某些不尽人意之处．一是机座下两个用硬塑料制成的皮带轮（主动和从动轮）强度较低，极易开裂损坏而导... “Critical Force Demonstrator” is a very practical teaching instrument because it is simple in structure, easy to operate, and can visually and intuitively demonstrate the relationship between centripetal force and particle mass, angular velocity and circle radius. When doing demonstration experiments, we found that the instrument also has some unsatisfactory features. One is that the two pulleys (active and driven wheels) made of hard plastic under the base have low strength and are easy to crack and damage.