A passenger of mass 70kg is seated in a roller-coaster car that passes through the lowest point of a vertical circular dip of radius 25m at a speed of 20ms−1. Ignore any vertical acceleration of the car other than the circular motion. Take g=9.8ms−2. What is the normal force exerted by the seat on the passenger at that instant?
a) 1.31kN
b) 1.8kN
c) 0.70kN
d) 2.44kN