A woman places her briefcase on the backseat of her car. As she drives to work, the car negotiates an unbanked curve in the road that can be regarded as an arch of a circle of radius 62.0 meter. While on the curve, the car's speedometer reads 15.0 m/s at the instant the briefcase starts to slide across the backseat toward the side of the car.
A) Find what force causes the centripetal acceleration of the briefcase when it is stationary relative to the car? Under what condition does the briefcase begin to move relative to the car?
B) Find coefficient of static friction between briefcase and seat surface?