A car driver stops at a traffic light when the light shows RED. A truck driver arrives at the traffic light just when it shows GREEN. He continues driving at a constant speed of 32 kmh-1. Suppose the road beyond the traffic light is straight and flat, how long will the car driver take to catch up with the truck, if he is driving at a constant acceleration of 2 ms^-2 in the direction of the truck ? Assume the average reaction time for a driver is 0.7 s
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Explanation:
let after t second the car driver take to catch.
speed of truck (Vt) = 32×5/18 = 80/9 m/s
=> distance covered by truck in time t
= distance covered by car in time t
=> Vt ×t = (1/2) at²
=> Vt = (1/2) at
=> 80/9 = (1/2)×2×t
=> t = 80/9 = 8.8888 S
since average reaction time = 0.7S
=> t = 8.8+0.7 = 9.5 S
hope this helps you
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