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# Find the angle in radian through which a pendulum swings if its length is 75cm and the tip describes an arc of length 15cm

$\begin{array}{1 1}(A)\;\large\frac{1}{2}\normalsize radian&(B)\;\large\frac{1}{3}\normalsize radian\\(C)\;\large\frac{1}{4}\normalsize radian&(D)\;\large\frac{1}{5}\normalsize radian\end{array}$

Toolbox:
• $\theta=\large\frac{l}{r}$
• $\theta$=angle subtended by arc
• $l$=length of the arc
• $r$=radius of the circle
Given :
Length =15cm
We know that $\theta=\large\frac{l}{r}$
$\Rightarrow \large\frac{15}{75}$ radians
$\Rightarrow \large\frac{1}{5}$ radians
Hence (D) is the correct answer.