Chapter 14: Answer Key – Mechanical Waves

Chapter 14 Mechanical Waves – Key

14.2 Properties of Mechanical Waves

1. 307 m/s

2. 1625 m  (≈ 1600 m)

3. 1.30 m

4.  λ _range = 0.017 to 17 m

5. 4.08 s (≈ 4.1 s)

6.  λ _air = 0.80 m    λ _water = 3.4 m    λ _aluminum = 10.9 m  (≈ 11 m)

7.  ∆ λ = 0.051 m

8.  v _ocean = 1462.24 m/s

14.3 Reflection, Refraction, and Diffraction

1. (i)  0.042 s   (ii)  0.021 m  or 21 cm    (iii) n  = 2.3  (two full constructive patterns)

2. n  = 3.57  (three full constructive patterns)

3. (i)  31.7° (≈ 32°)  (ii)  0.105 m (≈ 0.11 m)

4. 28.7°  (≈ 29°)

5. (i)  4.2 m & 1.1 m  (ii)  28° &  55.2°  (≈ 55°)

6. 41.8°  (≈ 42°)

14.4 The Doppler Effect and Shock Waves

1. 1328 Hz   (≈ 1.3 kHz)

2.  All hear the sound at the same time.

3. (i) 1319 Hz  (≈ 1300 Hz)   (ii) 1101 Hz  (≈ 1100 Hz)

4. (i) 1416 Hz  (≈ 1400 Hz)  (ii) 1020 Hz  (≈ 1000 Hz)

5. 1079 Hz  (≈ 1100 Hz) – 3238 Hz  (≈ 3200 Hz)

6. 227 m/s (≈ 230 m/s)

7. 14 286 Hz  (≈ 14 000 Hz) – 3030 Hz  (≈ 3000 Hz)

8. 165.5 m/s (≈ 170 m/s)

9.  ø = 24.6°  (≈ 25°)

10. Mach 1.89  (≈ Mach 1.9)

11.  ø = 3.0°

14.5.1 The initial test results in using sound to measure a vehicle speed.

(i) 23.1 m/s (≈ 23 m/s) to 25.8 m/s (≈ 26 m/s)

(ii) 7.6 %

(iii) 2.0 %