Sit on a chair and place your forearms on the top of a table. Raise your writing hand above the surface of the table in a way that it makes an angle of (no more than) 30-degree with the horizontal.
The Helper holds the yardstick
Now ask an assistant to hold the meter rule in a way that the zero at the bottom end of the meter stick is just above your thumb and index finger.
Position your thumb and index finger around both sides of the meter rule, making sure that your fingers do not touch the ruler. Tell your helper to release the ruler from your fingers suddenly, without your informing you.
The Ruler released
Once the ruler is released, try to catch it at the earliest possible by grabbing it between your index finger and thumb.
Grabbing the ruler
After holding the ruler, note the measurement on the ruler that are right above your thumb. Note this number and calculate the time taken through the distance formula; d = ½ gt2. Remember the value of g is 9.8 m/sec2 and the distance will be your measurement.