1. The problem statement, all variables and given/known data A roller-coaster car has a mass of 1050 kg when fully loaded with passengers. As the car passes over the top of a circular hill of radius 19 m, its speed is not changing. (a) At the top of the hill, what is the normal force (using the negative sign for the downward direction) FN on the car from the track if the car's speed is v = 8.7 m/s? (b) What is FN if v = 18 m/s? 2. Relevant equations fynet= mg-FN=ma a= v squared/r put together: FN= mg-mv squared/r 3. The attempt at a solution I've tried this problem and put g as -9.8m/s squared and got -14,472.9 for part (a) and used the same gravity again for part (b) and got -28,195.26... i also did use the postive g (+9.8) and got the wrong answers again. Is there something I am doing wrong?