PHYS4A/ Fall 2014; Moment of Inertia Pt. 1

Purpose: This experiment was done in order to find the moment of inertia of a spinning disk and to use that info in order to predict how long it would take for the cart to reach the bottom of the track.

For this experiment, a metal wheel was set up on a chair. A cart on rollers was set at an angle on a frictionless track and laid against the chair. For the experiment, we needed to calculate the moment of inertia for the spinning disk apparatus. This required the moment of inertia for not only the disk, but the two ends as well.

Calculations for the moment of inertia of the disk, two ends, and dimensions of the apparatus.

Once we found the moment of inertia, we were able to use Newton's Second Law to calculate the to find the translational acceleration of the disk.

Once the moment of inertia was calculated, acceleration was calculated

Once translational acceleration was calculated, kinematics were  used to determine the time that it
would take the cart to reach the bottom of the ramp which we calculated to be 8.27s. The experiment was then actually done in order to measure the time it took to go down the ramp by timing it with a stopwatch. 

Kim and Ivan timing the fall of the cart

It was recorded that it took 10 seconds to reach the bottom. This value was compared to the theoretical value of 8.27 s with a percent error of   17.3%. This could be due to the calculations not including frictional torque which would have given us a larger time needed. Thus the calculations do conceptually match the experimental data.