Maximum speed Tarzan can tolerate

[balletgirl]

Homework Statement

Tarzan plans to cross a gorge by swinging in an arc from a hanging vine. If his arms are capable of exerting a force of 1.4x10^3 N on the vine, what is the maximum speed he can tolerate at the lowest point of his swing? His mass is 80kg and the vine is 4.8m long.

Homework Equations

F=ma
v=(2pi*r)F

The Attempt at a Solution

I used the second equation to find v and ended up with 42,202 m/s, which seems way too high. I'm doubting this was the right equation to use since I didn't insert mass, and I'm not sure if 4.8m is the radius.

 

[balletgirl]

Nevermind, I redid the problem and it makes much more sense now.
I used f=ma, then a= F/m and got a= 17.5m/s^2. Then I used a=v^2/r and got v= 9.17m/s.