Question

A locomotive drive travelling at $72$ km/hr finds a signal $210$ meters ahead of him indicating that he should stop. He instantly applies brakes to stop the train. The train retards uniformly and stops $10$ meters before the signal post. What time did he take to stop the train?

• A. $5$ seconds
• B. $10$ seconds
• C. $15$ seconds
• D. $20$ seconds

Answer 1

The correct option is B $10$ seconds

To stop the train the driver has to cover 200 m at 72 km/hr.
$72km/hr=(72\times \frac{5}{18})m/sec=20m/sec.$
$\therefore$ Time taken to cover 200 m $=\frac{200}{20}seconds$
$=10seconds$