Rotating Reference Frames

Frame 1

Frame 2

Description

A ball is shown on a rotating merry-go-round with a frictionless surface. The ball starts at the center of the merry-go-round and moves outward at a constant speed. Views from two reference frames are shown, one where the motion of the ball is shown as seen from an observer on the ground and the other (shown above) where the motion of the ball is shown as seen from an observer on the merry-go-round.

Question

How do you write the laws of the physics so that both frames are correct? 


Instructor Resources

Answer: In order to get observers in the two reference frames to agree, we must invent a force that acts on objects in the accelerating frame. Here the accelerating frame is the rotating frame of the merry-go-round. An observer on the merry-go-round must invent a fictitious force to the right that causes the ball to accelerate to the right. Otherwise, the observer on the merry-go-round sees SF=0 and an acceleration, which violates Newton’s second law.
Script Author: Mario Belloni