A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in Fig.5.19. What is the action on the floor by the man in the two cases? If the floor yields to anormal force of 700 N, which mode should the man adopt to lift the block without thefloor yielding?

For this type questions the idea is to find the net force on floor.
In the first case the man apply a force of (25X10)N upward to lift the block, so by newtons 3^rd law a eqal and opposite force acts on floor = 25x10 N  so including the man’s weight it self we get a total of (25+50)x10 N force on floor.
in the second case in order to pull the body up by means of a pully he must apply a net force eqal to weight of body in downward direction there for floor will provide an eqal and opposite force upward there for net force on the floor = (50-25)x10 N, by doing this calculations we get first one as a force greater than 700N and second one leass than 700N, since the floor can only give a force of 700 N back the man should adopt the second method.  here I have takes value of “g” as 10 insted of 9.8

Thank u so much for answering....