A wheel having radius $10cm$is coupled by a belt to another wheel of radius $30cm$ . $1^{st}$ wheel increases its angular speed from rest at a uniform rate of$1.57 rad{s}^{–2}$ . The time for $2^{nd}$ wheel to reach a rotational speed of $100 rev/min$  is ____ $sec$. (assume that the belt does not slip)

$\left[\mathrm{Take} \mathrm{\pi }=3.14\right]$