Objects that slide or roll along curved tracks in a vertical plane are investigated in two separate experiments. One concerns a smooth metal nut that slides along a semicircular track made from coat hanger wire. The other concerns a billiard ball that slides and rolls along a curved track. A simple theoretical model is provided to account for the results and to extend the discussion to consider shortest descent times down circular tracks.

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See <https://physlets.org/tracker/> for this free software.
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