A simple pendulum consists of an object suspended by a
string of length l. The bob swings back and force. The
gravitational force, the weight (W), is resolved into
two components. The parallel component is along the direction of the spring.
The perpendicular component is at right angles to the direction of the spring.
When the bob is pulled to the right, the perpendicular component is to the
left, and vice versa. That is, the component of the weight (perpendicular),
is a restoring force. Further, for small angles (less than
15°) the magnitude of perpendicular component is
proportional to the displacement of the bob. Thus, small-displacement
pendulum motion is an example of simple harmonic motion.
T = 2p Ö l / |g|.
The period of simple pendulum of length l is given by an equation:
Note that for small-angle displacements, the period depends
only on the length of the pendulum, not its mass or amplitude. By measuring
the length and a period of a pendulum, we can find the magnitude of the local
value of gravitational acceleration, |g|.
The frequency of a pendulum is the number of complete cycles of motion in
one second. It can be found from the period using the equation:
f = 1 / T.