Physics Lab Equipment

LEMI-17 Apparatus of Shear Modulus and Rotational Moment of Inertia

LEMI-17 Apparatus of Shear Modulus and Rotational Moment of Inertia


  • Hall sensor and electronic timer

  • Specially designed metal claw to replace traditional metal disk

  • High accuracy

  • Affordable


The ratio of stress to strain within the elastic limit of a material is an important parameter of the material under load. The linear ratio of longitudinal stretch to the strain is known as the Young's modulus; while the ratio of shear stress to shear strain is called the shear modulus. Young's modulus and shear modulus have extensive applications in machinery, construction, transportation, and other industrial fields.


This apparatus of shear modulus and rotational moment of inertia (i.e. torsional pendulum) is designed with a specially designed hanging claw to replace the traditional disk plate. A rigid ring can be placed to the claw and rotates around the same axis in either horizontal or vertical state, while other shapes of rigid objects (such as rigid bars) can also be mounted onto the claw. The torsional swing is smooth and reliable. A Hall switch with magnet and digital timing device is used to measure the torsional swing period, check each half period time, and determine the optimal number of cycles for achieving accurate measurement results.


Various parameters such as period, moment of inertia, and diameter/length of a sample, can be accurately measured and calculated, yielding high measurement accuracy for the shear modulus of the material. This apparatus can measure rotational moment of inertia of rigid objects (such as rings, columns and bars) around different axes for the verification of the perpendicular axis theorem and parallel axis theorem.

Part List and Specifications 



Digital timing device Max counting number: 80; range: 0 ~ 255.99 s; resolution: 0.01 s 1
Hanging claw Length: 110 mm; width: 16 mm; rigid ring mounted vertically or horizontally 1
Hall switch senor DC 5 V 1
Support Triangular base, and clamp on the support rod 1
Rigid ring Inner diameter: 80 mm; outer diameter: 110 mm 1
Rigid square bar Length 120 mm; mass ~ 312 g 1
Rigid column bar Length 120 mm; mass ~ 187 g 1
Small steel ball 2
Small magnetic steel 1
String Steel string and copper string, diameter ~ 0.4 mm, 5 each 10

LEMI-17 Apparatus-1.jpg

  1. 1. Claw

  2. 2. Rigid Ring

  3. 3. Sample under Test

  4. 4. Hall Switch

  5. 5. Magnetic Steel

  6. 6. Base

  7. 7. Counting Timer

  8. 8. Indicator

  9. 9. Knob

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