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