Northern Caribbean University Mathematics & Eng. Dept. General Physics: PHYS 152 Assessment 1 Chapters 11 &12: Vibrations, Waves, Sound. Answer all Questions. Use g = 9.8 m/s2 Place answers in this document, creating space as needed. Provide a minimum of 4 references for Part 1 and a minimum of 4 references for Part 2. Name: ____________________________ ID#: ____________________________ Part 1: Concept Questions, 3 marks each; a. Define Simple Harmonic Motion b. Give three examples of everyday vibrating objects which exhibit SHM, at least approximately. c. What are the three requirements for the production of sound? d. If a pendulum clock is accurate at sea level, will it gain or lose time when taken to higher altitude? Why? e. If a child swings on a rope, how would the time for one swing be affected if the rope is lengthened? f. Give four everyday examples of resonance. g. When a sound wave passes from water to air what does not change? h. The intensity of a point source at a distance d from the source is I. What is the intensity at a distance 2d from the source? Part 2: Calculations, 5 marks each Calculate the following, clearly showing each solution. 1. If a body undergoes SHM with amplitude 1.4 cm, what is the total distance it travels in 8 periods? 2. Ariel dropped a block from a height of 40 m to the concrete pavement. If sound travels at 343 m/s what is the time interval between releasing the block and hearing the sound from the ground. 3. An elastic cord is 65 cm long when a mass of 75 g hangs from it, but is 90 cm long when a mass of 180g hangs from it. (a) What is the “spring” constant k of this elastic cord? (b) What is the period if it vibrates with the larger mass? 4. A piano tuner hears one beat every 2.0 s when trying to adjust two strings, one of which is sounding 440 Hz. (a) How far off in frequency is the other string? (b) If the speed of sound is 340 m/s what is the wavelength of the waves from the string with frequency of 440 Hz? 5. A boatman heard two distinct sounds 1.6 sec. apart, from an explosion at sea. If the speed of sound in air and water was 340 m/s and 1560 m/s respectively, how far away was the explosion? 6. An elastic cord vibrates with a frequency of 3.0 Hz when a mass of 0.60 kg is hung from it. What is its frequency if only 0.38 kg hangs from it? 7. A mass m at the end of a spring vibrates with a frequency of 0.88 Hz. When an additional 680-g mass is added to m, the frequency is 0.60 Hz. What is the value of m? 8. At what displacement from equilibrium is the speed of a SHO half the maximum value? 9. A sound wave in air has a frequency of 262 Hz and travels with a speed of 343 m s . How far apart are successive wave crests? 10. A tsunami of wavelength 300 km and velocity 750 km h travels across an Ocean. As it approaches land, people observe a decrease of sea level in the harbors. Approximately how much time do they have to run to safety?
