when a mass is falling throuh a height,first find the time required to reach the ground(plate)from the formula
s=1/2*g*t*t
in this g=9.8 mt/sec2,s=0.5 mt(in this problem)we will gwt the time as 0.3 sec.now we have to the potential energy as m*g*h this is equal to work done per unit time i.e...