Question

Robbers in a car travelling at 20 m/s pass a policeman on a motorcycle at rest. The policeman immediately starts chasing the robbers. The policeman accelerates at3 m/s for 12 s and thereafter travels at a constant velocity. Calculate the distance covered by the policeman beforehe overtakes the car.

Answer 1

Answer:

u=0,t=12sec,α=3m/s

2

Distance covered by police in 12secs

s=ut+1/2at

2

⇒0×12+1/2(3)(12)

2

⇒216m

v=u+at

v=36m/s

Distance travelled by robber in (12+t)sec

Distance =216+36t

Speed × Time=20(12+t)

2.16+36t=240+20t

t=1.5sec

Total time =12+1.5sec=13.5sec

Distance =216+36(1.5)

=216+54

=270m