Question

A rock is projected vertically upward. If it covers a distance of H/3 in the last second of its raise, then height H is

Answer 1

Velocity just after last second = 0 m/s
Velocity just before last second = u
Acceleration = -g

v = u + at
0 = u - g(1)
u = g

S = (v^2 - u^2)/(-2g)
H/3 = u^2/(2g)
H = 3u^2/(2g)
H = 3 × g^2/(2g)
H = 1.5g

Height H is 1.5g (where g = acceleration due to gravity).