As we know that time period of simple pendulum is given as
[tex]T = 2\pi \sqrt{\frac{L}{g}}[/tex]
here we know that
[tex]T = 3.8 s[/tex]
now from above equation we know that
[tex]T^2 = 4\pi^2(\frac{L}{g})[/tex]
now on rearranging the above equation we will have
[tex]L = \frac{gT^2}{4\pi^2}[/tex]
now plug in all data into it
[tex]L = \frac{(9.81)(3.8)^2}{4\pi^2}[/tex]
[tex]L = 3.6 m[/tex]
so the length of the cable must be 3.6 m
