Due to different tome intervals that we wish to measure, we need different types of clocks and watches. Watches and pendulum clocks can be used to measure long intervals of time, and stopwatches and ticker tapes measure short intervals of time.
Clocks are based on a regular event or process such as repetitive motion or vibration. Such motions are called oscillations. The time taken to complete one oscillation is known as the period of an oscillation.
Pendulum Clock
The clock is used to measure long intervals of time. It gives the hour, minute and second. The energy required for swinging comes from the coiled springs inside the clock or the gravitational potential energy of a descending mass.
Watch
Modern watches and clocks work based on the vibrations of the quartz crystals to keep time. Energy comes from a battery. They are also used to measure long intervals of time. However, some are based on coiled springs which need rewinding.
Stopwatch
Stopwatches are used to measure short intervals of time. There are two types: analogue which reads up to 0.1 s and digital which reads up to 0.01 s.
To measure a time interval, the stopwatch is manually operated by hand. This produces an error called human reaction time, which is about 0.3 s.
Ticker-tape Timer
This is an electrically operated devise that marks short intervals of time on to a tape in the form of dots. The timer is connected to an alternating electricity supply from the mains to cause the metal strip attached to the timer to vibrate50 times every second. By means of a carbon paper disc, the vibrating metal strip causes the paper tape that is pulled past the timer to record 50 dots in in one second. The time interval between two consecutive dots is 1/50 or 0.02 s. As such the ticker tape measures in intervals of 0.02 s . It is used in the determination of the acceleration of free fall, g .