A roller coaster car has a mass of 500 kg when fully loaded with passengers The car passes over a hill of radius 15 m as shown At the top of the hill the car has a speed of 8 0 m s What is the force of the track on the car at the top of the hill a 7 0 kN up b 7 0 kN down c 2 8 kN down d 2 8 kN up e 5 6 kN