Answer:
t =0.6
Explanation:
So this is just a basic kinematics where the only force acting on the ball is gravity (9.8 m/s2 [down] and air resistance is negligible.
∆d=vi∆t+1/2at2
Because you're dropping the ball, initial velocity is 0
1.5= 0*(∆t) + 1/2a*t2
After some rearranging, t= root ((2*∆d)/a) Therefore t= 0.5532833352 or root(15)/7 t=0.6s