^Cars on curved bridges

^Cars on curved bridges

Three identical cars A, B and C are moving at the same uniform, speed on three bridges. The car  A goes  on  a  plane  bridge, B on a  bridge convex  upward  and  C goes  on   a  bridge concave upward . Let  N_A, N_B and N_C be  the normal  forces exerted  by  the cars  on the bridges  when they  are at  the  middle  of  bridges.