Name: Zach Christoff
Lab Partners: Alyssa Jordan and Jake Hoffner
Date: 3/14/16
Lab Partners: Alyssa Jordan and Jake Hoffner
Date: 3/14/16
Purpose
To determine whether or not angular momentum is conserved with changes in angular velocity
Theory
The FBD below represents the rod, as well as the point masses, that was rotated. The dashed masses represent the ones that were moved to experience a change in velocity. The rod started spinning with the outermost dashed masses, but they were then pulled in closer towards the center, as shown by the diagram. Despite this change in velocity, angular momentum should still be conserved.
Experimental Technique
Any object spins with more angular velocity when more mass is centralized. Likewise, it spins with less angular velocity when more mass is farther from the radius. To test if angular momentum is conserved, I would need to have a clear cut change in angular velocity that would be measured in DataStudio. To do this, a string was tied to the innermost mass on the left side of rod, then looped through a plastic component of a robot, and finally tied to the innermost string on the right side of the rod. The excess string was brought to the middle, so when it is pulled up, the two innermost masses on both sides simultaneously move to the center. The "Before" picture shows the setup when the masses are on the outside. The "After" picture shows the masses when the are pulled to the center. When the masses are pulled to the center, like stated above, the rod begins to rotate faster. Of course, the rod has to actually be rotating for DataStudio to measure angular velocity.
DataStudio Measuring Angular Velocity and Change in Angular Velocity
Data
Analysis
Angular Momentum
Percent Difference of Angular Momentum
Kinetic Energy
Conclusion
The purpose of the lab was to show that angular momentum is conserved, and according to my numbers, angular momentum was definitely conserved. The percent difference of the initial and final angular momentum was 0.1849%, which is very minuscule, especially since the numbers and data are very small. With all of the small numbers and measurements, parallax error goes along with those measurements. Also, the point masses on the rod were said to have a mass of 0.0753 kg; however, the mass of each is slightly different and was neglected in the calculations. Because of the small percent difference, there are not many sources of error in this lab.
References
Bowman, Doug. "Conservation Lab." Lahs Physics. Web. 22 Jan. 2016.
Wolfs, F. L. H., and Douglas C. Giancoli. Student Study Guide & Selected Solutions Manual : Physics for Scientists & Engineers with Modern Physics,
Wolfs, F. L. H., and Douglas C. Giancoli. Student Study Guide & Selected Solutions Manual : Physics for Scientists & Engineers with Modern Physics,