NTA Abhyas JEE Main2020PhysicsWaves and SoundPractice
A massless rod BD of length l is suspended by two identical massless strings AB and CD of equal lengths. A block of mass m is suspended from a point P such that BP is equal to x . If the fundamental frequency of the left wire is twice the fundamental frequency of the right wire, then the value of l x is
Correct answer
5
Step-by-step solution
f ⁡ ∝ v ⁡ ∝ T ⁡ f ⁡ AB = 2 f ⁡ CD ∴ T AB = 4 T CD ...(i) Further Σ τ p = 0 ∴ T AB x = T CD ℓ - x or 4 x = l ⁡ - x T AB = 4 T CD or x = l ⁡ / 5 ⇒   l x = 5