Answer:
Width = 680 [m]
Explanation:
To solve this problem we must know the speed of sound in the air, conducting an internet search, we find that this speed has a value of v = 340 [m/s].
We apply the following kinematic equation, which relates space to time, to define speed.
v = x /t
where:
x = distance [m]
t = time [s]
v = velocity [m/s]
Now replacing:
x = 340 * 4
x = 1360 [m]
But the width of the cannon is calculated when the sound wave hits the wall of the canyon, so this width is half the distance.
Width = 1360 / 2 = 680 [m]