Question

a stuntman runs on a roof and without giving himself a vertical impetus, wants to land on another roof, 2m lower and 5m further horizontally. What is the minimal velocity he needs to run at?

Answer 1

In time t, he will drop 2 meters.
Thus, 2 = gt^2/2 = 4.9t^2 making t = .903sec.
Therefore, to travel forward 5 meters in t = .903sec., he must give himself an initial horizontal velocity of V = 5m/.903sec. = 5.533m/s.