A particle tied to a string of length R is projected from the lowest point with the minimum speed required to complete a vertical circle. Its speed when the string is horizontal is:
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Question

A particle tied to a string of length R is projected from the lowest point with the minimum speed required to complete a vertical circle. Its speed when the string is horizontal is:

G1 Physics · Accepted Answer

For minimum complete circle, bottom speed²=5gR. At horizontal position the particle has risen by R: v²=5gR−2gR=3gR.