Motion and Measurement of Distances: science class six
The SI unit: The International system of Units
In 1790, the French introduced a standard unit of measurement which has been accepted worldwide. This standard unit of measurement is called the metric system. The metric system of measurement is known as International System of Units also. The International System of Units is abbreviated as SI Unit in short.
Unit of Length
In SI Unit, the unit of length is meter and denoted by m generally.
1 meter = 100 centimeter (cm)
1 centimeter = 10 milimeter (mm)
The short lengths are measured in meter, centimeter, or millimeters.
But to measure long distances a unit kilometer is used and written as km in short.
1 kilometer = 1000 meter
Thus, we can measure the length of a desk, room, height of a person, length of clothes, etc. using meter and centimetre.
And we can measure the distance between two cities using kilometre. Although the distance between two cities can also be measured in meter or centimeter but that would not be convenient, so kilometre a bigger unit is used to measure a long distance.
Correct Measurement of Length
To find the correct length the use of the correct device and method both are necessary. In day to day life various types of measuring devices are used to measure the correct length.
A tailor uses measuring tape to measure the length of the cloth while a cloth seller uses a meter rod to measure the length of the cloth. Both types of devices, measuring tape and meter rod have their own importance.
A tailor uses measuring tape to measure the length of the arms of a person to stitch his cloth so can fit the person. And that very tailor uses a meter scale usually made of wood to mark the line on the cloth before cutting it. A meter rod would not be convenient for a tailor.
Similarly, for a cloth merchant measuring tape would not be convenient to measure the length of the cloth while selling it. Thus, a cloth merchant uses a meter rod to measure the length of the cloth.
In a similar way, the measuring tape will be suitable to measure the size of one's chest which cannot be measured using a meter rod.
We cannot measure the circumference of a tree using a meter rod. So in such a case measuring tape is convenient for it.
To measure the length of the line drawn on the notebook a small scale which is given in the geometry box will be more suitable. Similarly, to measure the length of a pencil the very scale which is given in the geometry box will be more suitable.
Correct Position of Eye while Measuring a length
Along with the device using the correct position of the eye is also necessary to measure the correct length.
While measuring the length of an object, say the length of a pencil, the position of the eyes must be exactly in front of the point where the measurement is to be taken. If the position of the eyes would be diagonal, then the result of the measurement would be slightly incorrect.
Hence, the position of the eye is as much necessary as choosing the correct device.
Measurement of the length of a curved line
The length of a curved line cannot be measured directly using a meter tape or a scale. Thus, to measure the length of a curved line we need at least two things, one thread, and one scale.
How to measure the length of a curved line?
* Draw a curved line on your notebook.
* Take a thread
* Make a knot at one end of the thread.
* Put the one end of the thread at which the knot is present at the one end of the curved line.
* Carefully place the thread along the line using your thumb and other fingers up to the end of the curved line.
* After reaching the end put a mark on the thread using a sketch pen.
* Now stretch the thread and measure its length using a scale or a measuring tape. In this case the scale would be more convenient.
* The length of the thread from the knot end up to the mark you put using the sketch pen will be the length of the curved line.
Reference: