If we assume that the fallen person is 60kg at a height of 20m.
The potential energy that hit the "hero" is:
PE = weight x gravity velocity x height
PE = 60 kg * 9.8 m/s^2 * 20m
PE = 11,760 Joules
(or) 11,760 newton of force
(or) 1,198 kg.f
Thus, the object exerts a force of 1,198kg upon hitting the "hero".
I like the detailed analysis... we need more of this