A man pulls his child up in a rope swing by throwing the lose end of the rope (the end without the child) over a branch and walking backwards away from the tree. The rope is 16 m long and the tree limb is 8 m above the man's center of gravity where he holds the rope. Suppose that the man begins at rest right next to the child and backs away with an acceleration of 0.2 m/s^2. Determine the speed of the child when he is 4 m above the man.