Time

Time is the duration of an event. Before watches and clocks were invented, people had to depend on primitive methods of measuring time. For instance, knots were tied at regular spaces on a length of rope. The rope was set alight at one end. In this way, one could measure hoe long an event took by the number of knots burnt. Similarly, incense sticks were used in Chinese rituals sometimes.

However, such methods gave inaccurate measurements of time. Over the centuries, man has developed more accurate ways of measuring time.

Question : Why do we need a standard unit of time?

Answer: Humans experience time differently depending on their surroundings or emotions. For example, doing absolutely nothing (besides breathing) for one minute might seem a long time. However, playing a computer game for one hour seems like a short time, especially when we are so engrossed in it.

Units of time

The S.i. unit of time is seconds (s). There are other units of time such as minutes (min), hour (h) and millisecond (ms).

Question: How do we measure time accurately?

Answer: There are instruments to help us measure time. Watches and clocks are everyday instruments that we use to measure the time. However, these are not sufficiently accurate for scientific purposes as they measure time to the nearest second. for example, To measure how fast a gas is given off during a chemical reaction. Therefore we need to use a stopwatch.

Stopwatches

There are two types of stopwatches, the mechanical one and the electronic one.

Mechanical stopwatches

The mechanical stopwatch has a minute scale and a second scale. The smallest division on the mechanical stopwatch is 0.1 seconds. Hence, it is accurate to 0.1s.

Using the mechanical stopwatch:

Step 1: Press the operating button to start the stopwatch.

Step 2: Press the operating button again to stop the timing.

Step 3: Press the reset button to reset the stopwatch back to zero. It is ready to be used again.

Electronic stopwatches

The electronic stopwatch is more accurate than the mechanical stopwatch. It can measure time intervals accurate to 0.01s. Unlike the mechanical stopwatch, it can also record the time interval in hours.

Using the electronic stopwatch:

Step 1: Press the start/stop button to start the stopwatch.

Step 2: Press the start/stop button again to stop the timing

Step 3: Press the reset button to reset the stopwatch.