(II) A source emits sound of wavelengths $2.64 \mathrm{~m}$ and $2.72 \mathrm{~m}$ in air. (a) How many beats per second will be heard? (Assume $T=20^{\circ} \mathrm{C}$.)

What are the wavelength and frequency of the fundamental standing wave in the tube?

Determine the length of an open organ pipe that emits middle C (262 Hz) when the temperature is $21^{\circ} \mathrm{C}$.

Two sound waves have equal displacement amplitudes, but one has $3.5$ times the frequency of the other. What is the ratio of their intensities?

Two sound waves have equal displacement amplitudes, but one has $2.6$ times the frequency of the other. (a) Which has the greater pressure amplitude and by what factor is it greater?

(II) You are trying to decide between two new stereo amplifiers. One is rated at $100 \mathrm{~W}$ per channel and the other is rated at $150 \mathrm{~W}$ per channel. In terms of $\mathrm{dB}$, how much louder will the more powerful amplifier be when both are producing sound at their maximum levels?

You are trying to decide between two new stereo amplifiers. One is rated at $75 \mathrm{~W}$ per channel and the other is rated at $120 \mathrm{~W}$ per channel. In terms of $\mathrm{dB}$, how much louder will the more powerful amplifier be when both are producing sound at their maximum levels?

A stone is dropped from the top of a cliff. The splash it makes when striking the water below is heard $3.5$ s later. How high is the cliff?

A stone is dropped from the top of a cliff. The splash it makes when striking the water below is heard 3.5 s later. How high is the cliff?

A stone is dropped from the top of a cliff. The splash it makes when striking the water below is heard $2.7 \mathrm{~s}$ later. How high is the cliff?

A 1750-N irregular beam is hanging horizontally by its ends from the ceiling by two vertical wires (A and B), each 1.25 m long and weighing 0.290 N. The center of gravity of this beam is one-third of the way along the beam from the end where wire A is attached. If you pluck both strings at the same time at the beam, what is the time delay between the arrival of the two pulses at the ceiling? Which pulse arrives first? (Ignore the effect of the weight of the wires on the tension in the wires.)

A sound wave is traveling in warm air $\left(25^{\circ} \mathrm{C}\right)$ when it hits a layer of cold $\left(-15^{\circ} \mathrm{C}\right)$ denser air. If the sound wave hits the cold air interface at an angle of $33^{\circ}$, what is the angle of refraction? The speed of sound as a function of temperature can be approximated by $v=(331+0.60~T) ~\mathrm{m} / \mathrm{s}$, where $T$ is in ${ }^{\circ} \mathrm{C}$.

A sound wave is traveling in warm air when it hits a layer of cold, dense air. If the sound wave hits the cold air interface at an angle of $25^{\circ},$ what is the angle of refraction? Assume that the cold air temperature is $-10^{\circ} \mathrm{C}$ and the warm air temperature is $+10^{\circ} \mathrm{C}$. The speed of sound as a function of temperature can be approximated by $v=(331+0.60 T) \mathrm{m} / \mathrm{s},$ where T is in ${ }^{\circ} \mathrm{C}$.

The velocity of waves on a string is $96 \mathrm{~m} / \mathrm{s}$. If the frequency of standing waves is $445 \mathrm{~Hz}$, how far apart are the two adjacent nodes?