Question

A ball thrown vertically upward from the ground level hits the ground after four secound calculate the maximum height reached during it's journey

Answer 1

top at 2 seconds
v = Vi -9.81 t
v = 0 at top at 2 s
so Vi = 9.81 * 2 = 19.6 m/s at takeoff
h = Vi t -4.9 t^2 = 19.6 * 2 - 4.9 * 4 = 39.2 - 19.6 = 19.6 meters at peak