A highway motorist travels at a constant velocity of 45Km /h in a 30Km/h zone . A motor-cyclist police officer has been watching from behind a bill board and at the Same moment the speeding motorist passes the bill board; the police officer accelerates uniformly from rest to overtake her. If the acceleration of the police officer is 10 km h-2 how long does betake to reach the motorist?

Let v be the velocity of the motorist = 45 km/h = 125 m/sit travels the distance d in time t.v = d/td = 12.5t ----(1)Policeman will cover the same distance in same time when start from rest with acceleration a = 10 km/h2 = 0.00077 m/s2d = ut + 12at212.5t = 0 +12×0.00077×t2t = 32467.5 st = 9.01 min

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