Answer
17.0 m/s
Work Step by Step
In this scenario, the mechanical energy $E_{mec}$ = K + U is conserved. At point A, the roller-coaster car is exactly at the same height as in the beginning, so U is the same as in the beginning and therefore also K (because K + U doesn’t change). Since K has the same value, the car must have the same speed $v_{0}$ = 17.0 m/s.
