What is the velocity acquired by a freely falling object 5 seconds after being dropped?

Take g = 9.81 m/s²
Take all downward quantities to be positive.

Initial velocity, u = 0 m/s
Acceleration, a = 9.81 m/s²
Time, t = 5 s

v = u + at
Final velocity, v = 0 + (9.81)(5) m/s = 49.1 s

v =u + gt
u is the initial velocity and g acts downwards.
It varies at different places. Only by a small amount on the earth. But it varies by a lot more on other bodies in space.
as an approximation if it is dropped from rest,
g ~= -9.8 m/s^2
so v = - 49 m/s
ie 49 m/s downwards.

Remember that you asked for VELOCITY not speed. So you MUST quote the direction to be correct.