Scale variation — lesson. Science CBSE, Class 7.

PUMPA - SMART LEARNING

எங்கள் ஆசிரியர்களுடன் 1-ஆன்-1 ஆலோசனை நேரத்தைப் பெறுங்கள். டாப்பர் ஆவதற்கு நாங்கள் பயிற்சி அளிப்போம்

Book Free Demo

In all the cases, the scale value may not be the same to plot a graph. Two different scales have to be chosen for the quantities on

$x$ -axis and

$y$ -axis, depending on the given data.

Motion of a bus

Here, the motion of a bus is taken as an example to plot a distance-time graph.

The time and the distance travelled by the bus is given in the following table.

Time ( $AM$ )	Odometer reading ( $km$ )	Distance ( $km$ )
$8$ $:$ $00$	$36500$	$0$
$8$ $:$ $30$	$36520$	$20$
$9$ $:$ $00$	$36540$	$40$
$9$ $:$ $30$	$36560$	$60$
$10$ $:$ $00$	$36580$	$80$

The total distance covered by the bus is

$80\ km$ . If a scale is chosen as

$1\ km$

$=$

$1\ cm$ , then an axis of length

$80\ cm$ should be drawn. But it is not possible to draw in a sheet of paper. So, a scale of

$10\ km$

$=$

$1\ cm$ can be used to show an axis of length

$8\ cm$ which is possible to draw in a paper. But, this graph covers only a small part of the graph.

Certain points to choose a suitable scale for drawing a graph:

the difference between the highest and the lowest values of a quantity.
the intermediate values of each given quantity, and
the utilisation of the maximum part of the paper.

Keeping these points in mind, a distance-time graph can be drawn with any value of scale.

To find the distance covered by a bus at $8$ $:$ $15$ $AM$ , a point ( $A$ ) is marked corresponding to the time on the $x$ -axis.
A perpendicular line ( $T$ ) is drawn to the $x$ - at $A$ so that they intersect each other.
A line parallel to the $x$ - intersects the $y$ - at the point ( $B$ ) is drawn through $T$ .
Thus, the line $OB$ gives the distance covered by the bus at $8$ $:$ $15$ $AM$ .

Shapes of graph:

The straight line in the distance-time graph represents that the object is in uniform motion. If the line is not uniform (curvy or irregular), then the object is in non-uniform motion.

Advantages of the distance-time graph

It provides information about the motion of any object, i.e., the distance moved at a definite time interval.
It helps to find the distance covered at any specific time interval.

Previous theory

Exit to the topic

Next exercise

Send feedback

Did you find an error?

Send it to us!

5. Scale variation

Theory: