Physics pendulum question, need help!

You and your friends find a rope that hangs down 15 m from a high tree branch right at the edge of a river. You find that you can run, grab the rope, and swing out over the river. You run at 2.0 m/s and grab the rope, launching yourself out over the river. How long must you hang on if you want to stay dry?

I'm not sure how to do this problem with a velocity given. Any help appreciated, thanks
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if you can use the small angle approximation, then you know that the period of a pendulum is

2 pi Sqrt[L/g]

if you can use the small angle approximation, then the period of this pendulum is

2 x 3.14 Sqrt[15m/9.8m/s/s] = 7.8s

the time from grabbing the rope to swinging out over the river to returning to your original position is half a period, so (if the small angle approximation is valid) the time you have to hold on is 3.9s

now, we can use the speed to determine if the small angle approx is valid

if your initial KE at the bottom of the swing is 1/2 m v^2, you will rise to a height of m g h

or h = v^2/2g = (2m/s)^2 / 2x9.8m/s/s = 0.20m

you can draw the situation and use trig to show that the maximum angle the rope makes with the vertical is approx 9.4 deg, so the small angle approx is valid and you can estimate the period from

2 pi Sqrt[L/g]