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Moment of inertia measured by three-wire pendulum

Moment of inertia measured by three-wire pendulum. School of Electronics & Applied Physics, Hefei University of Technology. Purpose of the experiment. 1. Master the principles and method of the moment of inertia measured by three-wire pendulum

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Moment of inertia measured by three-wire pendulum

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  1. Moment of inertia measured by three-wire pendulum School of Electronics & Applied Physics, Hefei University of Technology

  2. Purpose of the experiment • 1. Master the principles and method of the moment of inertia measured by three-wire pendulum • 2. Master the correct method of measuring the length, the quality and the time • 3. Learn to use the three-wire pendulum to measure the moment of inertia of disk and ring round the axis of symmetry • 4. Test Parallel axis theorem of the moment of inertia

  3. Instruments of experiment Three-wire pendulum, bubble level, steel tape measure, stopwatch, tested ring, cylinder under test

  4. Experimental principle Three-wire pendulum are constituted of the two disc A and B, both with uniform quality. With three lines which length is equal, B is hanging on the disc A. Three hanging points of each disc were connected to be an equilateral triangle which is inscribed circle. Shown in figure 1.

  5. When objects on disk and the disk rotating around the axis of symmetry, measure the moment of inertia with a three-disc, the formula isI=(mRrgT²)/(4²H) In the formula: m is the quality, R is the radius of the circumscribed circle constituted with the three hanging point of the up disc. r is the radius of the circumscribed circle constituted with the three hanging point of the down disc. T is the rotation of cycle of the down disc, H is the distance between the two disc.

  6. I1=[(m+M)RrgT²]/(4²H)-I0M is the quality of the ring, the ring is placed as the figure 2 shown. 1.Measure the moment of inertia of the disc with a three-disc, the formula is I0=(mRrgT²)/(4²H) M is the quality of the disc 2.Measure the moment of inertia of the ring with a three-disc, the formula is

  7. 3.Test the Parallel axis theorem of the moment of inertia, the formula is Id =0.5{[(m+2m1)RrgT²]/(4²H)-I0} M1 is the quality of the cylinder The cylinder is placed on the disc as the figure 3 shown. When the cylinder is circling the axis of symmetry, the formula is Id=0.5m1r1²+m1d²

  8. The connect and steps of the experiment 1.Adjust the three-wire pendulum 2.Measure the parameters of the instrument, they are l, R, r, rm, a, b, r1 3.Measure the moment of inertia of the disc 4.Measure the moment of inertia of the ring 5.Test the Parallel axis theorem of the moment of inertia

  9. Difficulty and Solution of the experiment 1.There are two kinds of instrument. Explain clearly the respective 2.The rotation angle of the disc can not be too much, because there is an assumptions that the rotation angle is small in the a derivative process. 3.The rotation system must be symmetrical.

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