A ball is attached to the end of a string hanging from the roof of a subway car. The train goes around a curve, turning to the left. You know that the car is traveling at 60 km/hr.

(a) Which way will the ball appear to swing?

(b) What force pushes the ball in that direction? If there is no such force, explain why the ball swings to the side even though there is no force pushing on it.

(c) If the ball swings at an angle of 15, what is the radius of curvature of the curve in the tracks?