1. The problem statement, all variables and given/known data In a loop-the-loop ride a car goes around a vertical, circular loop at a constant speed. The car has a mass m = 260 kg and moves with speed v = 15 m/s. The loop-the-loop has a radius of R = 10 m. What is the minimum speed of the car so that it stays in contact with the track at the top of the loop? 2. Relevant equations ac=v2/r F=ma 3. The attempt at a solution At the top of the loop, the forces acting on the car are Fgravity, FNormal, and Fcentrifugal (I think). So I think the minimum speed would be one that made all the forces cancel to zero (aka, Fc is just strong enough to counteract Fgravity and FNormal). If that's true, then Fc=FN+Fg. Since Fc=m*ac=v2/r , so far I have: m*ac=v2/r = m*g+m*g. ..but I don't think that makes sense... Is FN in this case equal and opposite to Fc?