Lab 19: Solid Ring Pendulum

Physics Lab #19 started on 6/1/15
Solid Ring Pendulum
Annemarie Branks
Professor Wolf

Objective: Determine the period of a pendulum ring.

Procedure:
     1.  Measure the inner and outer diameters of the ring with the vernier caliper. No need to weigh the ring because the masses will cancel out. For our little diameter, we measured 115.1 mm, and for the big diameter we measured 139.0 mm.

      2.  Notice the indent on the ring. The indent was made at the average of the two radii. This is where the ring will be swung on the rod. Using the moment of Inertia for a ring  about its center of mass, we can use the parallel axis theorem to find the moment of Inertia about the pivot. The moment of Inertia at the pivot was 0.00811 meters^2 * Mass of the ring. The calculations are shown below:

     3.  Using Torque=Inertia*angular acceleration, plug in your found Inertia and solve for angular acceleration. The constant in front of the sine theta is omega squared. Find your omega value. For us, it was 8.77 rad/s as seen in the above photo.

     4.  Now that omega has been found, the period can be found and ours turned out to be 0.717 seconds.

     5.  With the theoretical value found, set up the ring to swing at its indent on the rod. Place a photogate underneath it. A piece of paper or tape could be used if the ring does not pass through the photogate easily. With the photogate set up to LoggerPro, find the period. The period we go from LoggerPro was 0.719909 seconds which is pretty close to our theoretical value. We suspect there are sources of error since LoggerPro gave some variation of the period, but it always stayed around 0.72 seconds.