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Unformatted text preview: khounvivongsy (sk27799) Practice Problems 2 Weathers (17104) 1 This printout should have 36 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 3) 10.0 points You dip your finger into a pan of water twice each second, producing waves with crests that are separated by 0 . 11 m. Determine the frequency of these water waves. Correct answer: 2 Hz. Explanation: Let : n = 2 vibrations and t = 1 s . f = number of vibrations t = 2 1 s = 2 Hz . 002 (part 2 of 3) 10.0 points Determine the period of these water waves. Correct answer: 0 . 5 s. Explanation: T = 1 f = 1 2 Hz = . 5 s . 003 (part 3 of 3) 10.0 points Determine the speed of these water waves. Correct answer: 0 . 22 m / s. Explanation: Let : = 0 . 11 m . v = f = (2 Hz)(0 . 11 m) = . 22 m / s . 004 10.0 points The distance between two successive crests of a certain transverse wave is 1 . 50 m. Eight crests pass a given point along the direction of travel every 19 . 4 s. Calculate the wave speed. Correct answer: 0 . 618557 m / s. Explanation: Let : = 1 . 50 m , n = 8 crests , and t = 19 . 4 s . v = f = n t = 8 19 . 4 s (1 . 5 m) = . 618557 m / s . keywords: 005 10.0 points Earthquakes produce two kinds of seismic waves: The longitudinal primary waves (called P waves) and the transverse secondary waves (called S waves). Both S waves and P waves travel through Earths crust and mantle, but at different speeds; the P waves are always faster than the S waves, but their exact speeds depend on depth and location. For the pur pose of this exercise, we assume the P waves speed to be 8900 m / s while the S waves travel at a slower speed of 5150 m / s. Suppose a seismic station detects a P wave and then 80 . 3 s later detects an S wave. How far away is the earthquake center? Correct answer: 981 . 48 km. Explanation: Let : v P = 8900 m / s , v S = 5150 m / s , and t = 80 . 3 s . Suppose the earthquake happens at time t = 0 at some distance d . The P wave and the khounvivongsy (sk27799) Practice Problems 2 Weathers (17104) 2 S wave are both emitted at the same time t = 0, but they arrive at different times, re spectively t P = d v P and t S = d v S . The S wave is slower, so it arrives later than the P wave, the time difference being t = d v S d v P = d ( v P v S ) v P v S . Consequently, given this time difference and the two waves speeds v P and v S , we find the earthquake center being d = v P v S t v P v S = (8900 m / s) (5150 m / s) (80 . 3 s) (8900 m / s) (5150 m / s) 1 km 1000 m = 981 . 48 km . away from the seismic station. keywords: 006 10.0 points A wave is sent along a long spring by mov ing the left end rapidly to the right and keep ing it there. The figure shows the wave pulse at QR  part RS of the long spring is as yet undisturbed....
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This note was uploaded on 05/09/2010 for the course PHYS 1710 taught by Professor Weathers during the Spring '09 term at University of North Carolina Wilmington.
 Spring '09
 weathers
 mechanics

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