This lab is between a Level 2 and Level 3 inquiry activity in that it should be assigned after students understand acceleration but before they learn about the acceleration gravity. Because there are many sources of error when using a pendulum, students cannot be expected to determine the entire procedure on their own. Tips are given to reduce these errors without dictating the procedure. After this activity, students should clearly understand one way to determine the acceleration of gravity and have more experience using the pendulum equation.