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www.GOALias.blogspot.comYXFig. 13.14 Distance-time graph of the busGenerally, the choice of scales is notas simple as in the example given above.We may have to choose two different scalesto represent the desired quantities on thex-axis and the y-axis. Let us try tounderstand this process with an example.Let us again consider the motion ofthe bus that took Paheli and her friendsto the picnic. The distance covered andtime taken by the bus are shown inTable 13.5. The total distance coveredby the bus is 80 km. If we decide tochoose a scale 1 km = 1 cm, we shallhave to draw an axis of length 80 cm.This is not possible on a sheet of paper.On the other hand, a scale 10 km = 1cm would require an axis of length only8 cm. This scale is quite convenient.However, the graph may cover only asmall part of the graph paper. Some ofthe points to be kept in mind whilechoosing the most suitable scale fordrawing a graph are:• the difference between the highestand the lowest values of eachquantity.• the intermediate values of eachquantity, so that with the scalechosen it is convenient to mark thevalues on the graph, and• to utilise the maximum part of thepaper on which the graph is to bedrawn.Suppose that we have a graph paperof size 25 cm 25 cm. One of the scaleswhich meets the above conditions andcan accommodate the data of Table 13.5could beDistance: 5 km = 1 cm, andTime: 6 min = 1 cmCan you now draw the distance-timegraph for the motion of the bus? Is thegraph drawn by you similar to thatshown in Fig. 13.13?Distance-time graphs provide avariety of information about the motion154SCIENCE