Rotational Inertia Lab
Name: Kyle Collins
Lab Partner: Hunter McCabe
Date: 14 March 2015
Purpose: The purpose of this experiment is to investigate the relationship between moment of inertia of a spinning object.
Theory: The moment of inertia for a solid cylinder (the silver disk) can be found by using the equation I=(1/2)(m)(r squared). The black ring (or a hollow cylinder through the center) has a moment of inertia I=(1/2)(m)(r1 squared + r2 squared). For a rotating object accelerated by a pulley, the following equation needs to be used. Note that T is set equal to itself and then derived further.
Lab Partner: Hunter McCabe
Date: 14 March 2015
Purpose: The purpose of this experiment is to investigate the relationship between moment of inertia of a spinning object.
Theory: The moment of inertia for a solid cylinder (the silver disk) can be found by using the equation I=(1/2)(m)(r squared). The black ring (or a hollow cylinder through the center) has a moment of inertia I=(1/2)(m)(r1 squared + r2 squared). For a rotating object accelerated by a pulley, the following equation needs to be used. Note that T is set equal to itself and then derived further.
Experimental Technique: The device with the hanging mass was allowed to accelerate, one time with the disk and ring and one time with just the disk. The mass was set at a constant 30g. Angular acceleration was found using DataStudio. This was then used to find the moment of inertia using the equation derived above. It was then calculated for both objects using the geometric formulas listed above. Finally, these were compared with a percent difference equation.
Data and Analysis: Using the 30g mass, the angular acceleration for the disk and ring together was 10.5rad/s^2. With just the ring, it was 44.0rad/s^2. Using the derived equation for I, a value of .000681kgm^2 was calculated for the disk and ring; for just the disk, this value was .000148kgm^2. To find I for the ring, .000148 was subtracted from .000681, giving a value of .000533kgm^2. Using geometric formulas, moments of inertia for the disk and for the ring were .000137kgm^2 and .000504kgm^2, respectively.
Conclusion: This lab did show how one could calculate the moment of inertia in multiple ways. One source of error was that the rotary motion sensor also had a moment of inertia (as does any spinning object with mass) that was not accounted for in calculations. The disk was not completely round, and had slight protrusions on each side. Lastly, the string and pulley used to accelerate the system were not frictionless, accounting for more error.
References:
http://lahsphysics.weebly.com/moment-of-inertia-lab.html
Giancoli, D., & Giancoli, D. (2000). Physics for scientists & engineers with modern physics (4th ed.). Upper Saddle River, N.J.: Prentice Hall.
http://lahsphysics.weebly.com/moment-of-inertia-lab.html
Giancoli, D., & Giancoli, D. (2000). Physics for scientists & engineers with modern physics (4th ed.). Upper Saddle River, N.J.: Prentice Hall.