An elastic wire is found to be elongated by 1 cm when a mass is gently hung from it. It extends by 3 cm more, when the attached mass is made uniformly in a horizontal circle performing 2 rev s-1.The length of the unstretched wire (in cm) is

Q: An elastic wire is found to be elongated by 1 cm when a mass is gently hung from it. It extends by 3 cm more, when the attached mass is made uniformly in a horizontal circle performing 2 rev s-1 .The length of the unstretched wire (in cm) is (Given, g = 9.81 ms-2)

(a) $\frac{24-\sqrt{15}}{\sqrt{15}} \times 4 $

(b) $\frac{24}{\sqrt{15}} \times 4 $

(c) $\frac{4}{\sqrt{5}} $

(d) $\frac{4-\sqrt{15}}{2} $

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Ans: (a)