For the first problem you can use work and energy principals: the work done by the force 'F' acting over a distance 'd' equals the change in kinetic energy of the object:

For the second problem use energy principals again: change in potential energy + change in kinetic energy = 0. The potential energy he gains by attaining height 'h' is equal to mgh. His starting kinetic energy is (1/2)mv^2 and his KE at the top of the arc is 0, because at that point he is motionless. Now you can solve for 'h'.

For the third question I'm not following you, but in general the work done by the force of friction as the object slides horizontally must equal the initial KE when it first starts to slide on the floor, and that KE in turn must equal the loss of PE that occurred as it slid down the incline. So friction force = umg, and work by friction = umgd, which equals mgh. Hence d = h/u.