Force needed to pull oneself up with a pulley system at constant velocity

[murphy]

Okay, I have this crazy pulley question where a guy is sitting in a box that is attached to a pulley on the ceiling (the pulley system is ideal). He pulls himself up at a constant velocity -how do i find the force needed for him to pull himself up? (the rope goes around the pulley and back down to him- halfway around the pulley)
What about if he is accelerating upwards?

 

[Doc Al]

Identify all the forces acting on the "man + box" (treat them as a unit). Note that the man pulls down on one end of the rope, but both ends of the rope pull up on him. Apply Newton's 2nd law.

You may find this discussion helpful: https://www.physicsforums.com/showthread.php?t=46892

 

[murphy]

thanks! I got it! - I didn't realize that the man had double force pulling up on him!