Time SS1 Physics Lesson Note

Measurement of Time

Time is defined as the period in which a process, action or event takes place. Time is also called the Point or Period when something occurs. Time is an integral part of Physics and every single quantity in the physical world relies on it. 

Time has made the universe function simply and routinely. If time didn’t exist, there would be many irregularities in the schedule and timing of people. It is quite difficult to think of life when there is no time. There won’t be any physical quantities like acceleration, velocity and electromagnetic waves which depend on time for their existence.

The most natural time unit is the solar day which is manifested by the passing of day and night. It takes the Earth one solar day to complete one revolution about its axis.

1 day 24 hours

1 hour = 60 minutes

1 minute = 60 seconds

In the International System of Units (SI), the unit of time is the second (the symbol is s).

Types Of Clock/Watch

1. Ticker-tape timer:

This is used to measure short intervals of time accurately. It has a steel strip with a stylus which is controlled by an A.C. It vibrates 50 times in 1 second and makes use of a paper tape which helps in calculating the distance between the dots. The ce between the dots shows the distance ed by the body pulling the tape in cm. It is commonly used in motion and to practise the third law of motion. i.e., action and reaction are equal and opposite.

2. Stopwatch/Clock:

This is an instrument which is used to determine the time used either in the laboratory or on the field during sporting activities. It calculates both minutes and seconds. The second-hand makes one revolution in one minute.

3. Simple pendulum:

A pendulum is an instrument which is mostly used laboratory to measure time. The pendulum is right to left. The time taken or the time of oscillation is determined through this instrument.

The pendulum clock has a second hand made in the form of a pendulum. It oscillates to tick the minute’s hand and 60 oscillations of the second hand make 1 minute.

4. Heart-beat:

Heartbeat is a natural way of counting. It is mostly used in medical lines. The heartbeat gives the pressure and the rate of pumping of blood in the body. An increase in heart rate is an increase in blood pressure and vice versa.

5. Sand-clock:

Sand-clock is an instrument used in measuring time per hour. The instrument could still be designed to measure smaller intervals. The sand in the glass is made to run from the top bulb to the lower bulb through a small neck. It takes exactly one hour to complete one run. It is also called an hourglass.

Repetitive Events

A repetitive event is an event which keeps recurring every time. An example of a repetitive event is time. There are 24 hours in a day. This means that, after 24 hours which is a day, there is a reoccurrence of the event (time) to determine another day. The continuous counting of time makes a day, a month and a year.