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Figure shows a single degree of freedom system. The system consists of a massless rigid bar OP hinged at O and a mass m at end P. The natural frequency of vibration of the system is
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fn = 1 √ k 2π 4m -
fn = 1 √ k 2π 2m -
fn = 1 √ k 2π m -
fn = 1 √ 2k 2π m
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Correct Option: A
Force in the spring F = 2mg [from equilibrium] Deflection as mass at P, 
| x1 = | × 2a = 2x = 2 × | = | |||
| a | k | k |
| wn = √ | = √ | = √ | |||
| s | x1 | 4m |
| fn = | ωn = | = √ | |||
| 2π | 2π | 4m |
