To determine the distance between you on the ground and Superman in the air when you hear him, you can use the formula:
Distance = Speed × Time
In this case, the speed we are interested in is the speed of sound, which is given as 340m/s.
To find the time it takes for the sound to reach you, we need to calculate the time it takes for Superman's voice to travel from him to you.
Since he is moving at a constant speed of mach 4, which is four times the speed of sound, his speed is 4 × 340 m/s = 1360 m/s.
Now, we can calculate the time it takes for the sound to reach you by dividing the distance Superman has traveled (1 km or 1000 meters) by his speed (1360 m/s):
Time = Distance / Speed = 1000 m / 1360 m/s ≈ 0.735 seconds
Therefore, it takes approximately 0.735 seconds for the sound to reach you.
Now, to find the distance between you and Superman when you hear him, we multiply the speed of sound by the time it takes for the sound to reach you:
Distance = Speed of Sound × Time = 340 m/s × 0.735 s ≈ 249.9 meters
Therefore, when you hear Superman's voice, he is approximately 249.9 meters away from you in the air.