How Fast Must a Kid Go to Complete a Frictionless Loop-the-Loop?

[mohabitar]

We're analyzing this video here:
https://www.youtube.com/watch?v=ye3rF1MY9Ho

Radius of the loop is 1.17
No friction
Kid weighs 56.7 kg.
He starts from rest at the top of the ramp

What is the minimum tangential velocity required to successfully navigate the loop?

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So I did 1/2mv^2+mgh[top]=1/2mv[f]^2+mgh[loop]
The first 1/2m^2 cancels since v is zero.
The m's cancel out on all sides, and we're left with gh[top]=1/2v^2+gh[loop]
However, we have two unknowns in this equation: the height at the top of the ramp and the final velocity, so we can't solve. And the top height is not given to us. Am I missing something here? Am I doing this wrong?

 

[mohabitar]

Nobody? This seems like a simple one to help out with?

 

[bcguy015745]

well.. I am not sure but the way that i did the first question was that I used a free body diagram for when the dude was at the top of the loop.
so the only force acting on the dude would be gravity. so you can say that the force of gravity is equal to the force of centripetal acceleration, which means that
the net force is equal to mv^2/r
so...
mg=mv^2/r
v=sqrt(g*r)