1. The problem statement, all variables and given/known data A plane is travelling at 200 m/s following the arc of a vertical circle of radius R. At the top of its path, the passengers experience "weightlessness" .To one significant, what is the value of R ? 2. Relevant equations Mv^2/R=Mat , N=mg(1+at/g) Velocity orbit = squareroot(RG) 3. The attempt at a solution I try to use the velocity or orbit to this question until I saw the word " weightlessness" . That means there is apparent weight is zero but how could that apply to this case ? Does that mean N , apparent weight - mg=Mat , at is tangential acceleration ? and I consider N = 0 in this case. Does that make sense ? so F net = N-Mg=Mat and N=Mg(1+at/g) but N=0 , so at = -g and plug in to mv^/r =mat ?