# Quiz5a - Exam Phys 2C Name_Mechanical waves_ MULTIPLE...

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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) Waves on the surface of water are neither purely longitudinal nor purely transverse. 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) For waves with a given wave speed, higher frequency corresponds to lower wave number. 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) 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) When you tune a guitar, you change the tension of the strings, thus varying the speed of transverse waves on them. C) 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. D) 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. 3) Which of the following is a WRONG statement? A) 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. 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) In a longitudinal wave the speed of the wave and the speed of motion of material particles are different entities. D) 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. E) A smaller wave number corresponds to a greater distance between adjacent wave crests. 4) A simple harmonic wave with a frequency of 180 Hz and amplitude of 2 mm is propagating along a string in the negative x - direction at a speed of 55 cm/s. What is the wave number in m - 1 ? A) 300 B) 400 C) 2000 D) 600 E) 3000 5) A string, 60 cm long and having a mass of 71 g, is attached to a 770 - 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) 3.85 B) 121 C) 10.7 D) 270 E) 924 A-1

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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 (all in SI units): A) wavelength = 0.17 B) the maximal velocity of motion of a segment of the string
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## Quiz5a - Exam Phys 2C Name_Mechanical waves_ MULTIPLE...

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