A police officer observes a motorist who is approaching at a uniform speed of
80kmph. He, in his patrol car, starts chasing it as it just crosses him. After
accelerating for 8seconds at a constant rate, he attains his top speed of 120kmph. How
long does it take to overtake the motorist and at what distance?
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Answer:
Initial velocity of the motorist (u) = 120+80 = 200kmph = 55m/s
Final velocity (v) = 0
Acceleration (a) = 8m/s^2
Applying v^2-u^2=2as
0^2 - 55^2 = 2×8×s
3025 = 16s
S = 3025/16
= 189m
Applying S=ut+1/2at^2
189 = 55×t+1/2×8×t^2
189 = 59t
t = 3min 2sec
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