# Measurement of Time

Measurement of Time

In laboratory work, we often require measuring short time intervals of the order of few seconds. For this purpose, we use either a stopwatch or stop clock which makes use of periodic oscillations of a balance wheel or a pendulum clock which is based on periodic oscillations of a pendulum.

S.I unit of Time is second(s).

Other common units of time: minute, hour, day, month, year, decade, century and millennium.

Measurement of time period of a simple pendulum

To measurement of time period of a simple pendulum, the bob is slightly displaced from its mean position(rest position) and is then released. It begins to move to and fro about its mean position in a vertical plane. Now time for 20 complete oscillations is measured with the help of stopwatch and then dividing it by 20 which gives the time period of the simple pendulum.

Seconds Pendulum

A pendulum requiring exactly one second for each swing in either direction or two seconds for a complete vibration and having a length between centers of suspension and oscillation of 99.353 centimeters at sea level in latitude 45 degrees.