Physics 25 Section 2 Exam #1 February 1, 2012 Dr. Alward

Transcription

1 1.The tension in a taut rope is increased by a factor of 9, and the mass per length is reduced to one-fourth of its former value.. How does the speed of wave pulses on the rope change, if at all? A) The speed remains the same. B) The speed is reduced by a factor of 3. C) The speed is reduced by a factor of 9. D) The speed is increased by a factor of 6. 2.A wave is traveling at 35 m/s on a string with a linear density of kg/m. What is the tension in the string? A) 0.3 N B) 0.6 N C) 2.5 N D) 10.0 N 3.A bell emits sound energy uniformly in all directions at a rate of W. What is the intensity of the wave m from the bell? A) W/m 2 B) W/m 2 C) W/m 2 D) W/m 2 4.An ambulance emitting sound at 2000 Hz is racing at 30 m/s toward an automobile that is traveling in the same direction at 40 m/s. What frequency (in hertz) is heard by the driver of the automobile? The speed of sound is 343 m/s. A) 2056 B) 1625 C) 1904 D) Two timpani (tunable drums) are played at the same time. One is correctly tuned so that when it is struck, sound is produced that has a wavelength of 2.20 m. The second produces sound with a wavelength of 2.10 m. If the speed of sound is 343 m/s, what beat frequency (in hertz) is heard? A) 7 B) 9 C) 11 D) 13 Version 1 Page 1

2 6.Some of the lowest pitches attainable on a musical instrument are achieved on the world's largest pipe organs. What is the length of an organ pipe that is open on both ends and has a fundamental frequency of 8.75 Hz when the speed of sound in air is 341 m/s? A) 9.83 m B) 19.5 m C) 21.2 m D) 29.3 m 7.Four standing wave loops are observed on a string fixed at both ends as it vibrates at a frequency of 240 Hz. What is the fundamental frequency of the string? A) 23 Hz B) 28 Hz C) 35 Hz D) 60 Hz Use the following to answer question 8: Vibrations with frequency Hz are established on a 1.33-m length of string that is clamped at both ends. The speed of waves on the string is m/s. 8.How many antinodes are observed for the resulting standing wave pattern? A) 2 B) 3 C) 4 D) 5 9.A string with a linear density of kg/m and a mass of kg is clamped at both ends. Under what tension in the string will it have a fundamental frequency of 110 Hz? A) 270 N B) 310 N C) 450 N D) 580 N 10.A certain string, clamped at both ends, vibrates in seven loops at a frequency of Hz. What frequency will cause it to vibrate in four segments? A) 89 Hz Version 1 Page 2

3 B) 137 Hz C) 274 Hz D) 411 Hz 11.A tube open at one end, closed at the other, is 1.20 meters long. What is the frequency of a sound wave traveling at 340 m/s that would cause the sound waves in the tube to resonate with four nodes? A) 312 B) 403 C) 425 D) Two particles of the same mass carry charges +3Q and 2Q, respectively. They are shot into a region that contains a uniform electric field as shown. The particles have the same initial velocities in the positive x direction. The lines, numbered 1 through 5, indicate possible paths for the particles. If the electric field points in the negative y direction, what will be the resulting paths for these particles? A) path 1 for +3Q and path 4 for 2Q B) path 3 for +3Q and path 2 for 2Q C) path 4 for +3Q and path 3 for 2Q D) path 2 for +3Q and path 5 for 2Q E) path 5 for +3Q and path 2 for 2Q 13.Four point charges are placed at the corners of a square as shown in the figure. Each side of the square has length 2.0 m. Determine the magnitude of the electric field at the point P, the center of the square. Version 1 Page 3

4 A) N/C B) N/C C) N/C D) N/C 14.The figure shows the electric field lines in the vicinity of two point charges. Which one of the following statements concerning this situation is true? A) q 1 is negative and q 2 is positive. B) The magnitude of the ratio (q 2 / q 1 ) is less than one. C) Both q 1 and q 2 have the same sign of charge. D) The magnitude of the electric field is the same everywhere. E) The electric field is strongest midway between the charges. 15.The electric field measured by an observer 20 meters away from a positive point charge is 200 N/C. If the charge is doubled, and the observer moves 30 more meters farther away, what will be the new electric field measured by the observer, in N/C? A) 24 B) 49 C) 50 D) How many meters to the right of the negative charge below will the electric field be zero? The distance between the charges is 3.0 meters. Version 1 Page 4

5 A) The electric field is never zero anywhere to the right of the negative charge. B) 1.24 C) 1.45 D) For a diffraction horn loudspeaker, sound emerges through a rectangular opening. The opening of a diffraction horn has a width of 0.12 m. If the speaker emits a continuous tone with a wavelength of 0.02 m, within what angular width, i.e., the double angle, 2θ, is most of the sound emitted? A) 47 B) 39 C) 23 D) An ambulance with its siren emitting sound at a frequency of 2200 hertz is traveling at 40 m/s toward a car traveling toward the ambulance at 35 m/s. What is the frequency (in hertz) heard by the driver of the car? A) 2453 B) 2746 C) 2655 D) The intensity of a spherical wave 2.5 m from the source is 120 W/m 2. What is the intensity at a point 9.0 m away from the source, in W/m 2? A) 9.3 B) 24.2 C) 53.8 D) The speed of sound in a certain metal block is m/s. The graph shows the amplitude (in meters) of a wave traveling through the block versus time (in milliseconds, ms). What is the wavelength of this wave? Version 1 Page 5

6 A) 0.5 m B) 1.5 m C) 3.0 m D) 4.0 m Version 1 Page 6

7 Answer Key 1.D 2.D 3.A 4.B 5.A 6.B 7.D 8.C 9.A 10.B 11.C 12.E 13.D 14.B 15.D 16.B 17.D 18.B 19.A 20.D Version 1 Page 7