The period of oscillation of a pendulum is
[tex]T=2 \pi \sqrt{ \frac{L}{g} } [/tex]
Where L is the length of the pendulum and [tex]g=9.81 m/s^2[/tex] the gravitational acceleration.
Re-arranging the formula and using T=1.0 s, we find the length of the pendulum:
[tex]L= \frac{T^2g}{4 \pi^2}=0.25 m [/tex]
