16-Sept-2014: Circular Motion

Purpose
The purpose of this lab is for students to experience with rotational motion. Students are to find and calculate certain measurements with given information about the rotating object.
Apparatus
There are two part to this lab: the first is a rotating disk and the second is a motor that rotates a hanging object from a string that is attached onto a stick. The first part was done as a class, several students timed the period of each rotation, and the actual speed was measured by LoggerPro. The second part was done in groups and each group measured the time of each period as the professor monitored the motor and the speed of the rotation. To measure the angle, we used a stand with a piece of paper attached onto a bar. Students were to find the height of the stand, the distance of the stick from center, and the length of the string.

Explanation
The first part was to rotate a solid disk, which was spun by the professor, and the time was recorded by several students. As a class, we resulted with several different times, similar but different, and we averaged the time. With the average of the time, we then found the acceleration for the five trial rotations. Then we graphed an omega vs. acceleration plot chart and found that the correlation was close to the value of 1.

Before starting the second part of the lab, we solved for an equation that shows the relationship between omega and angle; as angle becomes larger, so does the omega. Each group were to find the time it took for a number of revolutions, and the class found the height of the hanging mass was measured from one student in the class. With the height of the hanging object, we were able to find the angle created from the string and hanging object. With the distance of the stick, the length of the string, and the angle, we measured omega with our equation. Comparing the measured omega and the actual omega, we get a correlation of 0.9851, and the percent error were below 4%.

Conclusion
Circular motion deals with omega and period, which are measurable. For period, we measured the time it takes for one revolution. For omega, it took a little more effort to find an equation that gives omega. We calculated an equation of omega depending on the angle, so we concluded from the equation that if the angle grows larger so does the omega.