Position time graph

It is easy to analyze and understand motion of an object if it is represented graphically. To draw graph of the motion of an object, its positions at different times are shown on y – axis and time on x – axis. For example, positions of an object at different times are given in Table 7.1.

Table 7.1 Position of different objects at different times

Time (s)	0	1	2	3	4	5	6	7	8	9	10
Position (m)	0	10	20	30	40	50	60	70	80	90	100

In order to plot position – time graph for data given in Table 7.1, we represent time on horizontal axis and position on vertical axis drawn on a graph paper. Next, we choose a suitable scale for this. For example, in Fig. 7.3, 1 cm on horizontal axis represent 2 s of time interval and 1 cm on vertical axis represent 20 m, respectively. If we connect different points representing corresponding position time data, we get a straight line as shown inFig. 7.3. This line represents the position-time graph of the motion corresponding to data given in Table 7.1.

We note from the data that displacement of the object in 1st second, 2nd second,………, 10th second is the same i.e. 10 m. In 10 second, the displacement is 100 m. Therefore, velocity is 100 m/10 s = 10 m/s for the whole course of motion.
Velocity during 1st second = 10 m/ 1s = 10 ms^-1
Velocity during 2nd second = 10 m/1s = 10 ms^-1 and so on.
Thus, velocity is constant i.e., equal to 10 m/s throughout the motion. The motion of an object in which its velocity is constant, is called uniform motion. As you see in Fig. 7.3, for uniform motion, position-time graph is a straight line.