6th Class Science Related to Competitive Exam Time

     Introduction

Time, distance and speed are the characteristics of moving objects. Speed of a moving object is determined by the time taken to travel a distance. Earlier, time of a day was determined by the position of the Sun, seen from the Earth in the sky. Later on, a time measuring device known as Sundial and water clock were used for the measurement of time. The standard unit of time is second and other unit of time is its derived unit. Distance is the shortest length between two points, two places, etc. The standard unit of distance is metre and others are its derived unit. The speed of a running object is determined by the division of distance by time. The unit of speed is meter per second and denoted by m/s. We have studied about the time, distance and speed in previous classes. In this chapter, we will learn detail about the time, distance and speed.

       Time

The duration of happening an event is measured in time, and its SI unit is second. Hour, minutes and other units are derived unit of time. Sundial, Sand clock and Water clock are the time measuring devices which were used in ancient days.

         Time Measuring Devices of Ancient Time

There were various types of time measuring devices in ancient world. The modern time measuring devices are based on the principle of ancient time measuring devices.

Look at the following pictures of ancient time measuring devices:

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Sundial was one of the most popular devices, used in ancient period. The name of sundial itself indicates that it is associated with the sun rays. Shadow of vertical blade on the division of the sundial shows the time of a particular period. Shadow of vertical bar is formed according to the position of the Sun in the sky. Sand clock consists of two glass bulbs which is joined by a narrow pipe. Upper bulb contains sand which flows downward till it gets empty.

Another ancient time measuring device was water clock. Function of water clock was same as that of sand clock, only water was used instead of sand. Water in the upper part of the clock flow downward and an empty upper part or a filled lower part of the clock was measured as one hour.

         Comparison of Different Units of Time

Time is measured in second but the other unit of time is derived unit as discussed above. There is some relation between the units of time with its standard unit. For example, 1 minute is l/60th of one hour and 1 second is 1/ 60th of 1 minute.

 Look at the following table of units and comparison of time:

      Give the name of the measuring instrument which was used for measuring the time in ancient time.

(a) Odometre

(b) Crystal watch

(c) Sundial

(d) All of these

(e) None of these

Answer: (c)

Explanation 

Sundial was used for the measurement of time in ancient time. Therefore, option (C) is correct and rest of the options is incorrect.

     Which one of the following is the standard unit for the measurement of time?

(a) Second

(b) Minute

(c) Hour

(d) All of these

(e) None of these

Answer: (a)

Explanation 

Standard unit for the measurement of time is second. Therefore, option (a) is correct and rest of the options is incorrect..