For different values of L, we get different values of $T^2$. The graph between L versus $T^2$ is as shown in figure. Find the value of ' g ' from the given graph. Take $(\left.{\pi }^2=10\right)$.

From the equation,

$T=2\pi \sqrt{\frac{L}{g}}$

We have,

$L=\left(\frac{g}{4{\pi }^2}\right)T^2\Rightarrow L\propto T^2$

i.e. L versus $T^2$ graph is a straight line passing through origin with slope = $\frac{g}{4{\pi }^2}$

Slope = $\tan \theta =\frac{g}{4{\pi }^2}$ or g= $\left(4{\pi }^2\right)\tan \theta$

$=\frac{4\times 10\times 0.98}{4}=9.8 \mathrm{m}/{\mathrm{s}}^2$