Answer
6.7 s
Work Step by Step
Here we use the equation $T=2\pi\sqrt {\frac{L}{g}}$ ; Where T - Period of the system, L - Measuring length from the suspension point to the center of the ball, g - gravitational acceleration.
$T=2\pi\sqrt {\frac{L}{g}}$
$T=2\pi\sqrt {\frac{l+R}{g}}-(1)$
We can write, $R=\frac{5.49\space m}{2}=2.745\space m-(2)$
$(2)=\gt (1)$ ; $T=2\pi\sqrt {\frac{8.4m+2.745m}{9.8m/s^{2}}}=6.7\space s$
Period of the system = 6.7 s
