12–139. cars move around the “traffic circle” which is in the shape of an ellipse. if the speed limit is posted at 60 km> h, determine the minimum acceleration experienced by the passengers. (60)2 y 2 0)2 = 1 *12–140. cars move around the “traffic circle” which is in the shape of an ellipse. if the speed limit is posted at 60 km> h, determine the maximum acceleration experienced by the passengers. 12–142. the race car has an initial speed va = 15 m> s at a. if it increases its speed along the circular track at the rate at = (0.4s) m> s2, where s is in meters, determine the time needed for the car to travel 20 m. take r = 150 m. x probs. 12–139/140