A bob attached to a string is released from horizontal position as shown in figure. For what value of $α$ (angle between string and vertical) during its motion, the total acceleration is directly horizontally?

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TestHub · Accepted Answer

Energy: m g ℓ cos α = 2 1 ​ m v 2 ⇒ a n ​ = ℓ v 2 ​ = 2 g cos α ; a t ​ = g sin α . Total acceleration horizontal gives tan α = a t ​ a n ​ ​ ⇒ tan 2 α = 2 , so cos α = 3 ​ 1 ​ - (C).

Physics - Circular Motion Question with Solution | TestHub

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