Shock Waves Printer Friendly Version
The one-shaped shock wave produced by a supersonic aircraft is actually the result of overlapping spherical waves of sound, as indicated by the overlapping circles in this physlet animation. Sketches a, b, c, d, and e, below show an "animated" growth of only one of the many spherical sound waves (shown as an expanding circle in the two-dimensional sketch). The circle originates when the aircraft is in the position shown in a. Sketch b shows both the growth of the circle and position of the aircraft at a later time. Still later times are shown in c, d, and e. Note that the circle grows and the aircraft moves farther to the right. Note also that the aircraft is moving farther than the sound wave. This is because the aircraft is moving faster than sound.

Careful examination will reveal how fast the aircraft is moving compared to the speed of sound. Sketch e shows that in the same time the sound travels from 0 to A, the aircraft has traveled from 0 to B, twice as far. You can check this with a ruler.

1. Inspect sketches b and d. Has the aircraft traveled twice as far as sound in the same time in these positions also?
2. For greater speeds, the angle of the shock wave would be
Refer to the following information for the next two questions.

3. Use a ruler to estimate the speeds of the aircraft that produce the shock waves in the two sketches below.
 Aircraft 3a is traveling about ____ times the speed of sound.

 Aircraft 3b is traveling about ____ times the speed of sound.

4. Draw your own circle (anywhere) and estimate the speed of the aircraft to produce the shock wave shown below.

 The speed is about ____ times the speed of sound.