Solution

Dik : For distance S₁ = h
V_o = 0 m/s
V_t = 10 m/s

V_t = V_o + at
20 = 0 + 10t
t = 0,5 second -> t₁

For distance S₂ = 1/2 h
t₁?

s = 1/2 gt²
t = √2S/g
t₂//t₁ = √2S₂/g//√2S₁/g=√S₂/S₁
t₂= √S₂/S₁.t₁
t₂= √1/2h/h . 0,5 second = √1/4 second