An engine is approaching a hill at a constant speed. When it is at a distance of 0.9km it blows a whistle whose echo is heard by the driver after five seconds. Find the speed of the engine if the speed of sound is 340m/s
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distance between hill and train = 900m
speed of sound = 340 m/s
distance covered in 5 sec by sound= 340 * 5 =1700 m
so,
the whistle sound first covers 900m towards the hill, and reflects as echo towards the train.
distance covered by echo = 1700 - 900= 800m
so, the train moves 800m before receiving the echo.
speed of engine = 800m/5sec =160m/s
speed of sound = 340 m/s
distance covered in 5 sec by sound= 340 * 5 =1700 m
so,
the whistle sound first covers 900m towards the hill, and reflects as echo towards the train.
distance covered by echo = 1700 - 900= 800m
so, the train moves 800m before receiving the echo.
speed of engine = 800m/5sec =160m/s
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