To see some of the trouble you can get into with noninertial reference frames, try this experiment. You and a friend stand opposite each other on the edge of a playground merry-go-round and get it rotating. While it is rotating, you attempt to toss a ball to your friend. As seen from above, what does the path of the ball look like

(a) to an observer standing at the top of a nearby slide,

(b) to you, and

(c) to your friend?

(d) If you did not know you were in a rotating reference frame, how would you explain the path of the ball in part b ?