1. A roller-coaster car has a mass of 1290 kg when fully loaded with passengers. As the car passes over the top of a circular hill of radius 20 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 = 9.3 m/s? (b) What is FN if v = 18 m/s? 2. F=mv2/r 3. I thought this was going to be a really simple question but apparently I can't figure out the answer. Here's what I did a) F=1290(9.3)2/20 = 5580N but for the answer I put -5580N cause of the part that says using the negative sign for the downward direction. I thought that was right b) F=1290(18)2/20 = 20900N but I changed it to -20900N for the same reason above.