Physics Chapter 4 Review Questions

10. Can a singer break a wineglass by singing loudly?

perhaps

3. What does n equal in Figure 4.5 (d)? How many wavelengths equal L?

11 nodes, L = 5λ or λ = L/5

6. A pipe with one open and one closed end has its lowest resonance at 200Hz. What are the frequencies of its next two resonances?

A closed pipe resonates with overtones that are odd multiples of the fundamental. If the fundamental is 200 Hz, the next two resonances are given by: f₃ = 3f1 = 3(200 Hz) = 600 Hz f₅ = 5f1 = 5(200 Hz) = 1000 Hz

8. In order to lower the Helmholtz resonances of a guitar, would you make the sound hole larger or smaller?

A larger sound hole produces a greater neck area, and therefore a higher resonance (see Helmholtz formula in chapter 2).

7. What is acoustic impedance?

Acoustic impedance is t the ratio of sound pressure to the volume velocity

9. To excite a singing rod in its fundamental mode, where should you hold it? Where should you stroke it?

Hold the rod at the center where the node is, stroke towards the ends

4. Distinguish between partials, harmonics, and overtones.

Partials, harmonics, and overtones are all components of sound. A partial includes the fundamental, plus the overtones, an overtone has a frequency greater than the fundamental, and a harmonic is a mode of vibration whose frequency is a whole-number multiple of the fundamental frequency.

11. What is the main function of a piano soundboard?

Radiation from a vibrating string is greatly enhanced by the sympathetic vibration of the soundboard.

1. Write a definition of resonance and give several examples

Resonance: When a vibrator is driven by a force that oscillates at a frequency at or near the natural frequency of the vibrator, and a relatively large amplitude results. Examples: Child on a swing, standing waves in a pipe or string.

5. If you blow over the ends of two pipes, one with the other end closed and one with it one, which pipe will give the tone of lower pitch? Approximately how much lower?

The closed end pipe will be one octave lower, because it vibrates with half the fundamental frequency.

2. 2. In Figure 4.4, do the solid curve or the dashed curves represent a higher Q? Explain.

The solid line has a higher Q value, the higher the damping, the less abrupt the phase change is, and therefore the lower the Q.