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A ball is slid directly outward from the center of a rotating merry-go-round with negligible friction. Viewed from the ground, what path does the ball actually follow?
AA path curved to the left
BA straight-line path
CA path curved to the right
DA tightening spiral inward
Answer & Solution
Correct answer: B. A straight-line path
1. Once released with negligible friction, no horizontal force acts on the ball, so by Newton's first law it must travel in a straight line as seen from the ground.
2. The curved path only appears in the rotating frame of the merry-go-round itself, where the surface turns underneath the straight-line path of the ball.
3. That apparent curve to the right, seen only in the rotating frame, is explained there using the fictitious Coriolis force.
4. A path curved to the left, a spiral inward, or any curve at all only make sense if described from the rotating surface, not from the ground.
_Source: OpenStax College Physics (CC BY 4.0), Ch 6 "Uniform Circular Motion and Gravitation", section 6.4 Fictitious Forces and Non-inertial Frames: The Coriolis Force_
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