here given that object is dropped from height h = 50 m
So here we can say
initial speed is ZERO
acceleration is due to gravity
now in order to find time to reach the ground we can use kinematics
[tex]y = v_i*t + \frac{1}{2}at^2[/tex]
now plug in all values in it
[tex]50 = 0 + \frac{1}{2} \times 9.8(t^2)[/tex]
[tex]t = 3.2 s[/tex]
so it will take 3.2 s to reach the ground