The radius of curvature of a loop-to-loop roller coaster is 12 m. At the top of the loop, the force that the seat exerts on a passenger of mass m is 0.4mg. Find the speed of the roller coaster at the top of the loop. Answer: v = 12.83 m/s. I assume .4 mg is the torque, right? I have no clue what to do. Please help.