In this physics lab activity students investigate how mass, length and angular displacement affect the period of a simple pendulum. Students control variables, testing one variable at a time, using manual techniques (stopwatch, human eye, etc). Data is graphed and compared to determine what variables affect period. Acceleration of gravity is also calculated and verified. The entire lab is then repeated using Vernier LabPro and Photogate in order to compare manual results with electronic results. A summary paragraph is written by students describing the affects of variables on period and the accuracy of manual techniques versus electronic techniques.