When a stretched wire of fundamental frequency $f$ is divided into three segments, the fundamental frequencies of these three segments are $f_1, f_2$ and $f_3$ respectively. Then the relation among $f_1, f_2, f_3$ and $f$ is (Assume tension is constant)

A steel wire of length 81 cm has a mass of $5 \times 10^{-3} \mathrm{~kg}$.

If the wire is under a tension of 50 N , then the speed of transverse waves on the wire is

The speed of a stationary wave represented by the equation

$$ y=0.7 \sin \left(\frac{7 \pi}{4} x\right) \cos (350 \pi t) \text { is } $$

(In the given equation $x$ and $y$ are in metre and $t$ is in second)

Two sound waves of wavelengths 99 cm and 100 cm produce 10 beats in a time of $t$ seconds. If the speed of sound in air is $330 \mathrm{~ms}^{-1}$, then the value of $t$ in seconds is