GATE 2021 CE (CE2) – Question 64
Level-road stopping sight distance is 140 m at design speed 90 km/h. Braking deceleration is 3.5 m/s² (g=9.81). Find perception/reaction time in seconds to two decimals.
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Show answer and explanation
Correct answer: 1.9 to 2.1
Explanation
Convert speed: 90/3.6=25 m/s. Stopping distance is $vt+v^2/(2a)$, so $t=[140-625/(7)]/25=2.028571$ s. **Answer: 2.03 s**. The given deceleration already includes braking friction, so g need not be used again.