In college physics experiments, a pendulum is often applied to measure the moment of inertia (J) of a rigid body. In this paper, we demonstrate a trifilar pendulum to determine not only J, but also the mass (m) of an irregular object. To this end, a standard weight is used to balance the pendulum, and a laser pointer is used to observe the amount of imbalance. According to the parallel axis theorem, a formula is deduced for the first time, which is related with m, J, oscillation period (T) of the pendulum, and the position (d) of the balancing standard. By the least squares fitting of a straight line to the experimental data of T ² ∼ d ², m and J can be obtained from the slope and intercept, respectively. It is found that the relative differences (between the experimental and theoretical values) of m and J are both less than 5.0% when four irregular objects (a tuning fork, a stainless steel meter ruler, an apple, and a bunch of keys) are tested. The reason for the difference and the improvement of this measuring system are discussed.

在大学物理实验中，通常采用摆来测量刚体的惯性矩（J）。在本文中，我们证明了三线钟摆不仅可以确定J，而且可以确定不规则物体的质量（m）。为此，使用标准砝码来平衡摆锤，并使用激光指示器观察不平衡的程度。根据平行轴定理，首次推导一个公式，该公式与m，J，摆的振荡周期（T）和平衡标准的位置（d）有关。通过对T ²的实验数据进行直线的最小二乘拟合〜d ²，米和Ĵ可以由斜率和截距分别获得。结果发现，当四个不规则物体（音叉，不锈钢米尺，一个苹果和一堆钥匙）被夹住时，m和J的相对差（实验值与理论值之间）均小于5.0％。经过测试。讨论了造成这种差异的原因以及该测量系统的改进。