Physics problem: help me.?

(a) KE = (1/2)mv^2, but this is produced by his giving up gravitational potential energy (mgh).  So you have
KE = mgh = (25 kg)(9.8 m/s^2)(1 m) = 245 J,
and v^2 = 2K/m = 19.6 m^2/s^2 => v = 4.4 m/s.

(b)  His impulse is the change in momentum, so it's 
(25 kg)(4.43 m/s) = 111 kg*m/s.
The average net force acting on him is (111 kg*m/s)/(0.5 s) = 222 N.
I have no idea what is meant by part (iii).