Question

Robbers in car travelling at 20 m/ s pass a policeman on a motorcycle at rest. The policeman immediately start chasing the robbers. the policeman accelerates at 3 m/ s 2 for 12 second and thereafter travels at a constant velocity. calculate the distance covered by the policeman before he overtakes the car.

Answer 1

Distance travelled by robbers = 20t Velocity at which policeman travel= V=u+at V=0+(3)12 V=36m/s Distance travelled by policeman in 12 sec = v^2 -u^2 = 2as (36)(36)= 2(3)s S= 216 m Distance travelled by policeman after 12sec= s = 36(t-12) S= 36t-432 Total distance travelled by robbers = total distance travelled by policeman after 12 sec 20t = 36t -432 t= 27 Distance travelled before overtaking the car is S = 20× 27 S= 540 m