Answer
$F=135 N$
Work Step by Step
We know that
$v=\sqrt{\frac{F}{\mu}}$
wher $'\mu'$ is Linear mass density
$v^2=\frac{F}{\mu}$
$\mu=\frac{F}{v^2}$
putting the values
$\mu=\frac{120}{170}=4.5\times10^{-3}\frac{kg}{m}$
For new tension, speed is given as $v=180\frac{m}{s}$
so from second equation, we have $F=\mu v^2$
putting the values
$F=(4.5\times10^{-3})(180)$
$F=135 N$
