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The diagram shows a wire \(ABCD\) consisting of a straight part \(AB\) of length \(5\) m and a part \(BCD\) in the shape of a semicircle of radius \(6\) m and centre \(O\). The diameter \(BD\) of the semicircle is horizontal and \(AB\) is vertical. A small ring is threaded onto the wire and slides along the wire. The ring starts from rest at \(A\). The part \(AB\) of the wire is rough, and the ring accelerates at a constant rate of \(2.5\) m s\(^{-2}\) between \(A\) and \(B\).
- Show that the speed of the ring as it reaches \(B\) is \(5\) m s\(^{-1}\).
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