PHY 1150
Chapter 14; Waves and Sound

D14.1 What is the wavelength of a 50 Hz wave when the wave speed is 340 m/s ?

D14.2 Consider a 9.0 m cable with a mass of 5.4 kg. When the cable is struck, a pulse moves down the cable and back in 0.6 s. What is the tension in the cable?

D14.3 Sketch the progression of two pulses shown here. The "top" one is moving to the right and the "bottom" one is moving to the left. Each pulse moves at 10 cm/s.

D14.4

Sketch the progression of two pulses shown here. The "short" one is moving to the right and the "tall" one is moving to the left. Each pulse moves at 10 cm/s.

D14.5 The A string on a violin is tuned to a fundamental frequency of 440 Ha. List the overtones that may be present in the audible range of frequencies.

D14.6 A guitar string 0.70 m long is tuned to play A at 440 Hz whe its full length vibrates. Where should a finger be placed in order to play C at 524 Hz?

D14.7 A demonstration is carried out with the apparatus shown here. A mass is suspended on one end of a string (so the tension in the string is the weight of the mas, mg). The string is then run over a pulley and attached to a small-amplitude 60-Hz oscillator. As additional masses are placed on the end, standing waves appear. The distance between pulley and oscillator is 2.4 m. That amoun of string has a mass of 45 g. How much mass is supported when the standing wave -- with three "loops" -- shown in the diagram is produced?

D14.8 With the string and arrangement shown in the problem above, what hanging mass is necessary to produce a standing wave of five "loops" if the distance from pulley to oscillator remains at 2.4 m?

D14.9 An organ pipe open at one end and closed at the other is 1.0 m long. What is its fundamental frequency? What is its first overtone frequency?

D14.10 A ringing tuning fork is held above a tube in a Physics experiment. The tube is filled with water whose level can be altered easily, thus changing the length of the column of air below the tuning fork. As the water level is lowered, lengthening the column of air, an increase in loudness is noted when the water is 0.120, 0.360, and 0.600 m from the top of the tube. Assume the speed of sound in air is 345 m/s. What is the frequency of the tuning fork?

This one should be (very) familar!

D14.12 A train whistle sounds at 500 Hz. What frequency is heard by a stationary observer when the train approaches at 25 m/s? When it moves away at 25 m/s?

What frequency is heard by a moving observer as she approaches the stationary train at 25 m/s? As she moves away from the stationary train at 25 m/s?

Take the speed of sound in air to be 340 m/s.

D14.13 A stationary train engineer sounds his own engine's horn, which has a frequency of 550 Hz, as another train passes. He notices a beat frequency of 2 Hz both as the train approaches and as it departs. What is the speed of the moving train? Take the speed of sound in air to be 340 m/s.