S = ut + 1/2gt²
where S = distance
50 cm = 0.5m
u is initial velocity = 0
S = 0*t + 1/2gt²
S = 1/2gt²
0.5 = 1/2 g (0.778²)
2*0.5 = g(0.778²)
1/(0.778²) = g
g = 1.65m/s²
The value of g is grossly errored due to the values obtained since the known value of g on earth is 9.8m/s² the obtained value rounds off to the value of g on moon.