To calculate the angular momentum vector of a counterclockwise rotating merry-go-round, use the formula L = Iω, where L is angular momentum, I is the moment of inertia, and ω is angular velocity. For a solid cylinder, the moment of inertia is calculated as I = ½mr², yielding I = 281.25 kgm² for a mass of 250 kg and radius of 1.5 m. Multiplying the moment of inertia by the angular velocity of 3.14 rad/s gives L = 884.0625 kgm²/s. The direction of the angular momentum vector aligns with the axis of rotation, pointing counterclockwise. Thus, the angular momentum vector of the merry-go-round is 884.0625 kgm²/s in the counterclockwise direction.