# The echo caused by a rifle shot reached the shooter 4 seconds after the shot.

**The echo caused by a rifle shot reached the shooter 4 seconds after the shot. At what distance from the shooter did the sound wave reflect if the speed of sound in air is 330 m / s?**

t = 4 s.

V = 330 m / s.

S1 -?

The wave velocity V is the ratio of the distance S traveled by it to the time t during which this distance was covered.

When fired, the sound wave from the gun travels the distance to the obstacle S1 and is reflected from it and, returning back, travels the distance S1 again. The sound wave travels the distance S = 2 * S1 in time t.

We express the speed of propagation of sound V by the formula: V = S / t = 2 * S1 / t.

The distance to the obstacle will be determined by the formula: S1 = V * t / 2.

S1 = 330 m / s * 4 s / 2 = 660 m.

Answer: the sound wave was reflected at a distance of S1 = 660 m from the shooter.