Pre Test 1. Name. a Hz b Hz c Hz d Hz e Hz. 1. d

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1 Name Pre Test 1 1. The wavelength of light visible to the human eye is on the order of m. If the speed of light in air is m/s, find the frequency of the light wave. 1. d a Hz b Hz c Hz d Hz e Hz 2. A 100-m long transmission cable is suspended between two towers. If the mass density is 2.01 kg/m and the tension in the cable is N, what is the speed of transverse waves on the cable? 2. b a. 60 m/s b. 122 m/s c. 244 m/s d. 310 m/s e m/s 3. If y = 0.02 sin (30x 400t) (SI units), the angular frequency of the wave is a. 30 rad/s b. 30/2π rad/s c. 400/2π rad/s d. 400 rad/s e. 40/3 rad/s 3. d 4. π For the transverse wave described by y = 0.15 sin (2 x 64 t) (SIunits 16, determine the maximum transverse speed of the particles of the medium. 4. b a m/s b. 0.6π m/s c. 9.6 m/s d. 4 m/s e. 2 m/s

2 y 1 y 5. Which of the following is a solution to the wave equation, =? x v t 5. b e x a. x sin x b. (cos kx) (sin t) c. e x sin ωt d. e x sin (kx ωt) e. e x cos t 6. Two ropes are spliced together as shown. 2 2 A short time after the incident pulse shown in the diagram reaches the splice, the ropes appearance will be that in (a) (b) (c) (d) 6. a (e) 7. A piano wire of length 1.5 m vibrates so that one-half wavelength is contained on the string. If the frequency of vibration is 65 Hz, the amplitude of vibration is 3.0 mm, and the density is 15 g/m, how much energy is transmitted per second down the wire? 7. d a. 21 W b. 11 W c. 5.4 W d. 2.2 W e. 1.1 W

3 8. Find the period of a wave of 100-m wavelength in deep water where 8. b v = gλ / 2π. a. 5.0 s b. 8.0 s c s d. 15 s e s 9. A piano wire of length 1.5 m vibrates so that one-half wavelength is contained on the string. If the frequency of vibration is 65 Hz, the amplitude of vibration is 3.0 mm, and the density is 15 g/m, how much energy is transmitted per second down the wire? 9. d a. 21 W b. 11 W c. 5.4 W d. 2.2 W e. 1.1 W 10. Calculate the intensity level in db of a sound wave that has an intensity of W/m c a. 20 b. 200 c. 92 d. 9 e The Young s modulus for aluminum is N/m 2. If the speed of sound in aluminum is measured to be 5.10 km/s, find its density (in kg/m 3 ). 11. c a b c d e

4 12. A point source emits sound with a power output of 100 watts. What is the intensity (in W/m 2 ) at a distance of 10.0 m from the source? 12. a a b c d e A car moving at 36 m/s passes a stationary police car whose siren has a frequency of 500 hz. What is the change in the frequency (in Hz) heard by an observer in the moving car as he passes the police car? (The speed of sound in air is 343 m/s.) 13. c a. 416 b. 208 c. 105 d. 52 e A truck moving at 36 m/s passes a police car moving at 45 m/s in the opposite direction. If the frequency of the siren is 500 Hz relative to the police car, what is the frequency heard by an observer in the truck after the police car passes the truck? (The speed of sound in air is 343 m/s.) 14. d a. 361 b. 636 c. 393 d. 396 e A wave generated in a medium is a longitudinal wave when 15. c a. there is a net transport of matter by the wave. b. the molecules of the medium are unable to exert forces on each other. c. molecular displacements are parallel to the wave velocity. d. molecular displacements are perpendicular to the wave velocity. e. the density of the medium is less than the density of water.

5 16. A plane wave propagating along the x-axis has the form 16. c 8π 2720π y( x,) t = ( cm ) sin x t. m s The frequency of the wave (in Hz) is 4 a b c d e. 2720π. 17. While you are sounding a tone on a toy whistle, you notice a friend running toward you. If you want her to hear the same frequency that you hear even though she is approaching, you must 17. c a. stay put. b. run towards her at the same speed. c. run away from her at the same speed. d. stay put and play a note of higher frequency. e. run towards her and play a note of higher frequency. 18. Drummers like to have high-pitched cymbals that vibrate at high frequencies. To obtain the highest frequencies, a cymbal of a fixed size should be made of a material 18. c a. with a low Young s modulus and a low density. b. with a low Young s modulus and a high density. c. with a high Young s modulus and a low density. d. with a high Young s modulus and a high density. e. composed of a metal-plastic laminate. 19. The variation in the pressure of helium gas, measured from its equilibrium value, is given by P = cos (6.2x 3000t) where x and t have units m and s, and P is measured in N/m 2. Determine the frequency (in Hz) of the wave. 19. b a b. 477 c d e. 239

6 20. Two tuning forks with frequencies 264 and 262 Hz produce beats. What is the beat frequency (in Hz)? 20. b a. 4 b. 2 c. 1 d. 3 e. 0 (no beats are produced) 21. Two waves are described by 21. b y 1 = 6 cos 180t and y 2 = 6 cos 186t, (both in meters). What effective frequency does the resultant vibration have at a point? a. 92 Hz b. 183 Hz c. 6 Hz d. 3 Hz e. 366 Hz 22. The superposition of two waves 22. e y1 = (0. 006cm )cos2 π t and y2 = (0. 004cm )cos2 s π t s at the location x = 0 in space results in a. beats at a beat frequency of 3 Hz. b. a pure tone at a frequency of 153 Hz. c. a pure tone at a frequency of 156 Hz. d. beats at a beat frequency of 6 Hz in a 153 Hz tone. e. a tone at a frequency of 156 Hz, as well as beats at a beat frequency of 6 Hz in a 153 Hz tone. 23. Which of the following wavelengths could NOT be present as a standing wave in a 2 m long organ pipe open at both ends? 23. d a. 4 m b. 2 m c. 1 m d m e. 0.5 m

7 24. Two harmonic waves are described by y1 = (3m )sin x t m s 24. d y 2 = (3m )sin x t 2 m s What is the amplitude of the resultant wave? a. 8.0 m b. 4.3 m c. 6.0 m d. 3.2 m e. 3.0 m 25. Two harmonic waves traveling in opposite directions interfere to produce a standing wave described by y = 2 sin (4x) cos (3t) where x is in m and t is in s. What is the speed (in m/s) of the interfering waves? 25. a a b c. 1.3 d. 12 e A string is stretched and fixed at both ends, 200 cm apart. If the density of the string is g/cm, and its tension is 600 N, what is the wavelength (in cm) of the first harmonic? 26. b a. 600 b. 400 c. 800 d e. 200

8 27. Two waves are described by 27. c y 1 = 6 cos 180t and y 2 = 6 cos 186t, (both in meters). With what angular frequency does the maximum amplitude of the resultant wave vary with time? a. 366 rad/s b. 6 rad/s c. 3 rad/s d. 92 rad/s e. 180 rad/s 28. Two strings are respectively 1.00 m and 2.00 m long. Which of the following wavelengths, in meters, could represent harmonics present on both strings? 28. c a , 0.670, b. 1.33, 1.00, c. 2.00, 1.00, d. 2.00, 1.33, 1.00 e. 4.00, 2.00, Two identical strings have the same length and same mass per unit length. String B is stretched with four times as great a tension as that applied to string A. Which statement is correct for all n harmonics on the two strings, n = 1, 2, 3? 29. d a. f n,b = 4 1 fn,a. b. f n,b = 2 1 fn,a. c. f n,b = 2 f n,a. d. f n,b = 2 f n,a. e. f n,b = 4 f n,a. 30. Which of the following wavelengths could NOT be present as a harmonic on a 2 m long string? 30. d a. 4 m b. 2 m c. 1 m d m e. 0.5 m