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Unformatted text preview: Exam Phys 2C Name__Mechanical waves_________________________________ MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Which of the following is a WRONG statement? A) When you play a guitar and clamp a string with your finger, you produce a note with a different frequency, because you change the wave speed. B) Light waves propagate faster than sound waves. Therefore, if a sound wave and a light wave have the same frequency, the sound wave has a smaller wavelength. C) Waves on the surface of water are neither purely longitudinal nor purely transverse. D) Two small amplitude harmonic waves propagating on the same string should have the same wave speed. 2) Which of the following is a WRONG statement A) If a spherical wave propages in a medium without losing its total power, its intensity varies as an inverse square of the distance from the wave source. B) Two waves along the x axis producing disturbances y(x, t) = 3 · sin(2x 3t) and y(x, t) = 8 · sin(4x 6t) have different wave speeds. (Here x is the position, t is the time, and all coefficients are in SI units.) C) If the amplitude of a wave on a given string is reduced to a half, while the frequency and the tension force remain unchanged, the power of the wave is reduced to a quarter. D) When you tune a guitar, you change the tension of the strings, thus varying the speed of transverse waves on them. 3) Which of the following is a WRONG statement? A) A smaller wave number corresponds to a greater distance between adjacent wave crests. B) The equation y(x, t) = A · exp[ (x bt) 2 ] corresponds to a bell shaped pulse running in the positive x direction with a wave speed b. C) For waves with a given wave speed, higher frequency corresponds to lower wave number. D) The wave speed of a pulse can be measured as the distance traveled by the crest of the pulse divided by the time its takes to travel this distance. E) In a longitudinal wave the speed of the wave and the speed of motion of material particles are different entities. 4) A simple harmonic wave with a frequency of 230 Hz and amplitude of 1 mm is propagating along a string in the negative x direction at a speed of 45 cm/s. What is the wave number in m 1 ? A) 1400 B) 2200 C) 5500 D) 1200 E) 3200 5) A string, 80 cm long and having a mass of 61 g, is attached to a 660 Hz vibrator at one end. The other end of the string is fixed and the string is kept under tension. The vibrator produces a transverse wave in the string, whose amplitude is 5.0 mm, and that propagates with a velocity of 32 m/s. The energy of the wave is absorbed at the fixed end. In this situation, the tension in the string, in SI units, is closest to: A) 87 B) 78 C) 75 D) 81 E) 84 A1 6) The equation y ( x,t ) = 0.02 sin(6 x + 144 t ), where all quantities are in SI units, represents a traveling wave on a string having: A) wavelength = 38 B) the maximal velocity of motion of a segment of the string = 2.88 C) frequency...
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This note was uploaded on 12/13/2011 for the course PHYS 2C PHYS 2C taught by Professor Groisman during the Spring '11 term at UCSD.
 Spring '11
 groisman

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