Measurement of Length
There are different methods to measure the length.
At a medical shop, people measure their height.
In our school life we have used different items like scale for measurement of length.
Let’s study the different methods to measure the length.
Let's define the meaning of the length.
Length is defined as the distance between the two points.
For Example, the one end of eraser is at zero of the scale and other end is at the 5cm. So its length will be 5cm.
cm is centimeter. units of length.
There are two methods to measure the length. One is Direct method and another is Indirect method.
When we can reach both the ends of length, the measurement is done by direct method.
In direct method instruments used are meter scale, screw gauge and Vernier caliper.
Meter scale is an instrument that has numeric calibrations on it to measure length.
Screw gauge is used for measuring the cylindrical and spherical objects
The Vernier Caliper is a measuring device.
It is more accurate than the meter scale.
Now, Screw gauge is a measuring device that uses the concept of pitch and circular scale.
Now, we will study the indirect methods to measure the length.
The large distances such as the distance of planet or sun from the earth cannot be measured directly with meter scale.
So, for measurement of long distances we use the parallax method.
In parallax method, to measure the distance
$D$
of a far away planet
$S$
.
We observe the planet
$S$
from two different positions
$A$
and
$B$
on the earth separated by a distance
$AB=b$
.
And the distance from the earth is calculated using the given formula as above.
Next, we will see the Echo method for measuring the large distances.
Here, we send the wave (sound or light) towards the object and the reflected wave is again received.
This method is used in aircraft and ship.
The formula for distance is given as above.
Revision
The formula for calculating the distance using RADAR method is given as,
In direct method instruments used are meter scale, screw gauge and Vernier caliper.
In parallax method the formula for calculating the distance of planet is as above.
That’s all…Learn and share…