1. What is the weight of this objects?
Weight is simply the product of mass and gravitational acceleration. Therefore the weight is:
w = 20 kg * 9.81 m/s^2
w = 196.2 kg m/s^2 = 196.2 N
2. After 5 seconds, how has the object fallen and what is its speed at this instant?
We can use the formula:
y = v0 t + 0.5 g t^2
v = v0 + g t
where v0 = 0 since the object starts from rest, y is the distance it fell, t is time
y = 0 + 0.5 * 9.81 * 5^2 = 122.625 m
v = 0 + 9.81 * 5 = 49.05 m/s