Tosional Pendulum

  • Supervisor: Dr. Yongkang Le
  • Location: Room 804 West Annex of Guanghua Building


  • This experiment is designed for the review of the rotation of rigid body.


Related topics

  • Rotational motion
  • Oscillatory motion
  • Elasticity


  A torsional pendulum, or torsional oscillator, consists usually of a disk-like mass suspended from a thin rod or wire. When the mass is twisted about the axis of the wire, the wire exerts a torque on the mass, tending to rotate it back to its original position. If twisted and released, the mass will oscillate back and forth, executing simple harmonic motion. This is the angular version of the bouncing mass hanging from a spring. This gives us an idea of moment of inertia. We will measure the moment of intertia of several different shaped objects. As comparison, these moment of intertia can also be calculated theoretically.We can also verify the perpendicular axis theorem. Given that the moment of intertia of one object is known, we can determine the torsinal constant K.

Experiment devices

Schematic diagram of the experiment device


  1. Familiarize yourself with the operation of the device. Adjust the device carefully so that it is ready for the measurement.
  2. Determine the torsinal constant K of the spiral spring with a plastic cylinder. Employ the theoretically calculated moment of inertia of the plastic cylinder as a known value.
  3. Measure the moment of inertia of differently shaped object. Compare the measured results with the theoretically calculated values.


  1. On which factors is the moment of inertia dependent?
  2. What are the causes that may bring error to our measurement?


  1. 沈元华,陆申龙, 基础物理实验 (Fundamental Physics Laboratory) 高等教育出版社 北京 2004 pp. 100-103
  2. Ravitej Uppu, Torsional Pendulum

Lab Manual


Sir,For the laboratory report, I have some problem on calculating the uncertainty because I don't know the uncertainty value of the electronic balence. Any suggestion?
Similar to the example in the “Introduction Lecture”, we take 0.1g for d and 0.2g for a. Would you please inform your classmates this message? Thank you very much! — Le Yongkang 2010/03/20 18:14
I would like to tell them, thanks for replying….
course/fund_phy_exp/tosional_pendulum.txt · 最后更改: 2018/03/09 21:49 由 xiaole
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