The multiflash photograph in Figure A shows two balls falling from rest. The vertical rulers are marked in centimeters. Use the equation s=490t^2 (the free-fall equation for s in centimeters and t in seconds) to answer the following questions:
a) How long did it take the balls to fall the first 160 cm? What was their average velocity for the period?
The Attempt at a Solution
square root of (160/490)
My question is how do you find the average velocity? Do you take the derivative of the first equation which would be 490t and plug 160 cm in again?