The time of one full swing of a simple pendulum; it depends only on the length and the gravitational acceleration — not on the mass or the amplitude.
Symbols
T
period of oscillation
[s]
L
length of the pendulum
[m]
g
gravitational acceleration
[m/s²]
Where it comes from
The period depends only on the length and on g, not on the mass nor (for small displacements) on the amplitude — this is the isochronism of the pendulum. A longer pendulum swings more slowly.
When to use it
A simple pendulum at small displacements; determining g.
Example
Calculate the period of a pendulum of length 1 m (g=9.8).