Vf - Vo = gT
where
Vf = velocity of apple just before hitting the ground
Vo = initial velocity of apple = 0
T = time for apple to hit the ground = 1.5 sec (given)
g = acceleration due to gravity = 9.8 m/sec^2 (constant)
Substituting appropriate values,
Vf - 0 = 9.8(1.5)
Vf = 14.7 m/sec.
