Course:PHYS341/Archive/2016wTerm2/Assignments/A2

Reading Assignment 2 (Jan 16 for quiz on Jan 20)
Read sections 4.1-4.4, 5.1-5.4, 6.1-6.5 in the textbook.

Quiz 2 practice questions

1. Circle any of the statements below that are true.

Longitudinal waves -
(a) can occur only in gases
(b) can occur only in liquids and gases
(c) can occur in solids, liquids and gases ✓
(d) can transmit energy permanently from one place to another ✓
(e) can transmit matter permanently from one place to another

2. A small sound source radiates sound waves at one frequency equally in all directions. The wavelength is determined by the sound speed in the medium. The sound speed is determined by the stiffness and density of the medium. Stiffer media (all else being equal) have higher sound speeds. More dense media (all else being equal) have lower sound speeds. As the wave radiates outward the wavelength may change (but only if the medium does), but the frequency does not. As the wave radiates outward the amplitude becomes smaller - even without damping - as the sound energy is spread over an ever growing area.

Use only the following words to fill in the blanks (some words may be used more than once):
amplitude, energy, frequency, higher, lower, velocity, unchanged, wavelength

3. Circle any of the statements below that are true.

Beats are an acoustic phenomenon in which -
(a) you hear the individual pressure oscillations of a sound wave
(b) two sound waves with vastly different frequencies add together to make a sound with an audibly oscillating amplitude
(c) two sound waves very close in frequency add together to make a sound with an audibly oscillating amplitude ✓
(d) two sound waves go in and out of phase with each other causing the amplitude to rise and fall ✓
(e) two sound waves interfere with each other ✓

4. Circle any of the statements below that are true and go together to create the best correct explanation.

If I blow over the top of a beer bottle I produce sound at a certain frequency. If I add some water to the bottle and repeat, the frequency will
(a) rise ✓
(b) fall
(c) stay the same

because

(a) the water is less dense than the glass
(b) the length of the air column in the bottle is reduced
(c) the volume of air in the bottle is reduced ✓
(d) the mass of air in the neck has not changed

and

(a) it is easier to squeeze a smaller body of air a certain amount than a larger one by the same amount
(b) it is harder to squeeze a smaller body of air a certain amount than a larger one by the same amount ✓
(c) it is no harder, or easier, to squeeze a smaller body of air a certain amount than a larger one by the same amount

5. Circle any of the statements below that are true.

An object (string, air column, soundboard etc.) is said to have a natural frequency.
(a) If it is vibrated at this frequency it will vibrate with a larger amplitude than at any other frequency. ✓
(b) If it is vibrated at any random frequency it will still vibrate at its own natural frequency.
(c) If it is struck (with a solid object or a jet of air) it it will vibrate at the natural frequency. ✓
(d) The natural frequency is a property of the object alone. ✓
(e) The natural frequency is a property of the object and whatever has excited it.
(f) An object can have only one natural frequency.