Robbers in a car travelling at 20 ms−1 pass a policeman on a motor cycle at rest. The policeman immediately starts chasing the robbers. The policeman accelerates at 3 ms−2 for 12 s and thereafter travels at a constant velocity. Calculate the distance covered by the policeman before he overtakes the car.

Given 

For Policeman

A= 3 ms−2

V=12*3=36ms-1

For Robbers

V=20ms-1

Solution:--

Let at time T Policeman catches the Robbers.

Distance(S) travelled by Robbers=20t

Distance(S) travelled by the Policeman=1/2*at^2+at(t-12)

[Distance covered by Robbers=Distance covered by Policeman]

On puttuing a value

=>20t=1/2*3*12*12+36(t-12)

=>20t=216+36t-432

=>t=27/2

Therefore

Distance(S)=20*t=20*27/2=270m

Thats your answer

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