METHOD OF MEASUREMENT OF DIFFERENT PHYSICAL QUANTITIES (3)

Measurement of time


Time is measured by a wall clock, wrist watch, table clock. To measure a

fraction of time , stop watch is used.



Method of measurement of time by a clock


In our day to day life , time is measured by pendulum clock, whose function is based on the oscillation of a pendulum. In this type of clock, a metal rod is suspended from a rigid support. A heavy metal ball is suspended from the end of the rod. The time taken by the metal ball in one oscillation is regarded as 1 second. It consists of a circular dial which divided in 60 equal divisions.

Each division represents 1 minute. It is further divided into 12 equal parts, where each parts represents 1 hour. Hours are marked from 1 to 12 . In this clock long arm is the arm of minute and the short arm is the arm of hours. A spring is wound up with the help of key in old type of clock and by battery in digital clocks or battery operated clocks. The potential energy is converted to kinetic energy and rotates the arms of the clock.



Method of measurement of interval of time with the help of stop watch


Stop watch is used to measure the time interval between two events. It consists of a circular dial which is divided in 60 equal divisions. Each division represents 1 second. A long, light needle called second’s hand pivoted at the centre, rotates over the circular scale. A big circular dial also contains a small circular dial to read the time in minutes . The smaller dial graduated in 30 or 60 divisions and the small needle called the minute’s hand rotates over the scale. When the seconds hand completes one rotation, the minutes hand moves through one division or 1 minute.

A knob is provided at the top of the frame for winding the watch. By pressing the

Knob in succession, the watch can be started, stopped and both the needles can be

Brought to searting point for future use.