Question

29. A stationary railroad whistle is sounded. An echo is heard 5.0 seconds later by the train’s engineer. If the speed of sound is 343 m/s, how far away is the reflecting surface? A) 68 m C) 860 m E) 2000 m B) 140 m D) 1700 m

Answer 1

Answer:

830 is ur answer

Explanation:

hope this helps u

Answer 2

Answer:

The distance between the train and the reflecting surface is 860 m.

Explanation:

The sound emitted by the whistle travels across the distance L between the train and the reflecting surface, and then for another L to come back to the train. This means that the time $t = 5.0 \: s$ between the whistle and the echo corresponds to the time the sound takes to cover a total distance of 2L. Assuming the sound moves by uniform motion with speed $v = 343 \: m/s$,the basic relationship between distance covered, time and velocity:

$S = vt = (343) \times (5) = 1 715 \: m.$

This distance corresponds to twice the distance between the train and the reflecting surface $(S=2 L)$

=> $L = \frac{S}{2}$

=$\frac{1715}{2}$

= 857.5 m.

The distance between the train and the reflecting surface L = 857.5 m = 860 m (approx)