CONCEPT OF TIME AND ITS MEASUREMENT

Time is defined as the duration of an event and its measured in seconds. Measurement of time works on the principle of constant oscillation. The standard unit of time is seconds (s).

Examples of measuring devices are

1. Ticker - Tape Timer

2. Stop watch / clock

3. Sand clock

4. Simple Pendulum

5. Heart - Beat

Ticker Tape Timer

The Ticker Tape Timer is a piece of apparatus that we use to measure time. 

It makes dots on a paper tape. The amount of dots depends on its frequency. 

Ticker Tape Timer

Note:

We have to count the number of SPACES and not the number of dots themselves to measure the time taken. 

The first dot at the direction of movement is the starting dot.

Example:

A ticker tape timer makes 40 dots in 1 second. The result of an experiment to find the average speed of a toy car is shown below.

What is the average speed of the toy car?

Answer:

time = 1/40 * 10 = 0.25 s

speed = 0.6 / 0.25 = 2.4 m/s

STOP WATCH / CLOCK

A stopwatch is used to measure the time interval of an event.

Types of stopwatch 

1.  Digital stopwatch 

2.  Mechanical stopwatch 

How to read Digital stop watch?

It is commonly used in laboratories,it can measure a time interval up to 0.01 second.It starts to indicate the time lapsed as the start/stop button is pressed.As soon as start/stop button is pressed again,it stops and indicates the time interval recorded by it between start and stop of an event.A reset button restores its initial zero setting.

How to read analog or Mechanical stopwatch

A mechanical stop watch can measure a time interval up to 0.1 second.It has a knob that is used to wind the spring that powers the watch.It can also be used as a start stop and reset button.The watch starts when the knob is is pressed once.When pressed second time,it stops the watch while the third press brings the needle back to zero.

SAND CLOCK OR HOUR GLASS

An hourglass (or sandglass, sand timer, or sand clock) is a device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated trickle of material from the upper bulb to the lower one. Factors affecting the time interval measured include sand quantity, sand coarseness, bulb size, and neck width. Hourglasses may be reused indefinitely by inverting the bulbs once the upper bulb is empty. Depictions of hourglasses in art survive in large numbers from antiquity to the present day, as a symbol for the passage of time.

SIMPLE PENDULUM

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

Pendulum clock has seconds hand made in form of the pendulum.It oscillates in order to tick the minute hand and 60 oscillations of the seconds hand makes a minute.

HEART - BEAT

Heart beat is a natural way of counting. It is mostly used in medical line. The pumping of blood in the body. An increase in heart beat is an increase in blood pressure and vice versa.