It is necessary to know that the gravity of the earth accelerates objects at a rate of 9.8 meters per second squared and then use the laws of gravitation formulated by Isaac Newton
The distance that an object travels under constant acceleration is given by the formula:
distance = 1/2 × acceleration × time2 + intial speed × time
The initial speed is zero because the balls are dropped and not thrown. Therefore, we can solve for time:
time2 = (2 × distance) / acceleration
Substituting distance = 54 meters and acceleration = 9.8 meters/second2, we get
time2 = (2 × 54 meters) / (9.8 meters/second2) = 11.0 seconds2
The square root gives:
time = 3.3 seconds