These magnitude and direction problems always give me a really hard time! What other numbers should I have in order to solve this problem? Hopefully from that I will be able to figure out the proper equation to use. Thanks! Q: A roller coaster car of mass 320 kg (including passengers) travels around a horizontal curve of radius 30 m. Its speed is 18 m/s. What is the magnitude and direction of the total force exerted on the car by the track?