At the county fair, Carrie and Sam climbed up on the carousel horses. Around and around they went; the horses also bobbed up and down. When they got off of the carousel, Carrie told Sam they had been accelerating during their ride. Sam disagreed; they had been moving at a constant speed. Whose response is fully correct, and why?

I believe sam's response is correct.
When human is riding a moving target with constant speed over a period of time, we tend to have a visual acceleration perception due to our optical movement.
This make people such as Carrie believes that the carousel horses are accelerating while it actually stayed at constant pace.

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