Measuring g: Motion in One Dimension
Catch a Meter Stick
PIRA Class: 1C30.55

Purpose
To calculate a student's reaction time using the distance that a meter stick falls and the local known value for acceleration due to gravity

Description
A student holds out vertically before himself a meter stick. He releases the meter stick and then immediately regrasps the meter stick to stop its fall. The time it takes for him to catch the meter stick is his reaction time.
1. Hold meter stick vertically, grasped somewhere in the middle, noting a reference point for its initial position (e.g., index finger's position)
2. release and then immediately regrasp meter stick; note new reading of the index finger
3. Calculate the time fof the fall using: d=1/2gt^2 (I.e., t=sqrt(2d/g)
NOTE: Local acceleration due to gravity is 9.84 m/s^2
VARIATION: Have students time (using stop watches) their fellow students' reaction time. Compare these reaction times with the calculated reaction times - discuss the difference. You could start this activity using the dollar bill drop (where a student can keep the dollar bill if they can catch it. Practice first!)

Equipment
Meter stick