A small test car of mass \(0.20 \text{ kg}\) moves along the inside of a vertical circular track of radius \(R = 2.5 \text{ m}\). Assume friction between the car and track is negligible and the acceleration due to gravity is \(g = 10 \text{ m/s}^2\). What is the minimum speed the car can have at the highest point of the track without losing contact with the surface?