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www.GOALias.blogspot.com(b) Sand clock(a) Sundial at Jantar Mantar, Delhi(c) Water clockFig. 13.5 Some ancient time-measuring devicesFig. 13.6 Measuring the speed of a ballMeasure the distance between the pointat which the ball crosses the line andthe point where it comes to rest. Youcan use a scale or a measuringtape. Let different groups repeat theactivity. Record the measurements inTable 13.3. In each case calculate thespeed of the ball.You may now like to compare yourspeed of walking or cycling with that ofyour friends. You need to know thedistance of the school from your homeor from some other point. Each one ofyou can then measure the time takento cover that distance and calculate yourspeed. It may be interesting to know whoamongst you is the fastest. Speeds ofsome living organisms are given in149MOTIONAND TIME149