Solution:
Given
Radius, r = 7m
The formula for calculating the length of an arc is
[tex]\begin{gathered} l=\frac{\theta}{360}\text{ x 2}\pi r \\ \end{gathered}[/tex][tex]\begin{gathered} \text{But }\theta=180^0(Given) \\ l=\frac{180}{360}\text{ x 2}\pi\text{ x7} \\ l=7\pi \end{gathered}[/tex]