Question:
Find the angle in radians as well as in degrees through which a pendulum swings if its length is 45 cm and its tip describes an arc of length 11 cm
Solution:
We know that l = r × θ
Here $I=$ length of $\operatorname{arc}=11 \mathrm{~cm}$
$\mathrm{R}=$ radius $=$ length of pendulum $=45 \mathrm{~cm}$
We need to find $\theta$
$11=45 \times \theta$
$\theta=\frac{11}{45}$ radian
$\theta$ in degree $=\frac{11}{45} \times \frac{180}{\pi}=\frac{44}{22 / 7}=14^{\circ}$