Question

Two identical piano wires kept under the same tension T have a fundamental frequency of 600 Hz. The fractional increase in the tension of one of the wires which will lead to occurrence of 6 beats/s when both the wires oscillate together would be(a) 0.02(b) 0.03(c) 0.04(d) 0.01

Answer 1

We want one of the wires to alter the frequency by 6 Hz  = 0.01 or 1%

   frequency f = √[ T /μ ]

relative errors:    Δf/f = 1/2 *  ΔT/T  + 1/2 * Δμ /μ

Δf / f = 0.01   =>   ΔT/T = 0.02       as  μ = constant.

The fractional increase 0.02 or  2%

Hope it is helpful....