This sounds like a simple kinematics question in physics. To begin, we see that the flower pot is "knocked off" as opposed to thrown down, so we can assume the initial velocity in the y-direction equals zero (vi=0). We also know that the acceleration of gravity is a constant (g=-9.8m/s^2). And the last piece of information we have is t=5sec. We can use a kinematics equation that contains all of these known values, and final velocity as our unknown:
vf = vi + gt
vf = (0) + (-9.8m/s^2)(5s) = -49m/s
Remember, the final velocity has nothing to do with mass (the experiment where we drop a marble and a bowling ball at the same height and same time, we notice that they hit the ground at the same time!).
Knowing this, for the second part of the problem, the final velocity will be the same as when the mass = 1kg.