A ball is thrown vertically up, its speed slowing under the influence of gravity. Suppose

(a) we film this motion and play the tape backward (so the tape begins with the ball at its highest point and ends with it reaching the point from which it was released), and

(b) we observe the motion of the ball from a frame of reference moving up at the initial speed of the ball. The ball has a downward acceleration g in

BLUE: (a) and (b).

YELLOW: only (a).

GREEN: only (b).

PURPLE: neither (a) nor (b).