There's no need to use a mass in there, and the force F isn't 9.81 m/s^2 as explained above; the force F would be given by F = m*a here, not just F = a = 9.81 m/s^2. If you set it up with F = m*a, where m is 62 kg and a = 9.81 m/s^2 you get:
F = m*a = (m*v^2)/r (not (m*v)^2)
From here we can see that we've got the constant mass m on both sides, so we divide by m on both sides to remove it from the equation:
a = (v^2)/r
We can solve this for v to get the equation I mentioned above by multiplying by r on both sides and taking the square root of both sides:
v = sqrt(a*r)
It's again important to note here that 1 g is not a force (given in Newton with unit kgm/s^2) but rather an acceleration (given in g where g = 9.81 m/s^2), if that makes any sense.
